CN113539598A

CN113539598A - Rare earth magnet and method of making the same

Info

Publication number: CN113539598A
Application number: CN202110234458.3A
Authority: CN
Inventors: 佐久间纪次; 庄司哲也; 木下昭人
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2020-04-21
Filing date: 2021-03-03
Publication date: 2021-10-22
Anticipated expiration: 2041-03-03
Also published as: RU2755198C1; KR102417738B1; JP7298533B2; US20210327620A1; US11664140B2; EP3901967B1; KR20210130095A; JP2021174818A; CN113539598B; BR102021006354A2; EP3901967A1

Abstract

The present invention relates to rare earth magnets and a method for making the same. A rare earth magnet having a main phase and a grain boundary phase, the overall composition is represented by the formula (R ² _(1‑x) R ¹ _x ) _y Fe _{(100‑y‑w‑z‑v)} Co _w B _z M ¹ _v ·( R ³ _(1-p) M ² _p ) _q ·(R ⁴ _(1-s) M ³ _s ) _t (wherein, R ¹ is a light rare earth element, R ² and R ³ are medium rare earth elements, and R ⁴ is a heavy rare earth element Rare earth elements, M ¹ , M ² , and M ³ are predetermined metal elements.) means that the main phase has a core, a first shell, and a second shell, and the first shell is more in the first shell than in the core. , the content ratio of medium rare earth elements is high, the content ratio of medium rare earth elements is lower in the second shell portion than in the first shell portion, and the second shell portion contains heavy rare earth elements.

Description

Rare earth magnet and method for producing same

Technical Field

The present disclosure relates to a rare earth magnet and a method of manufacturing the same. The present disclosure particularly relates to an R-Fe-B-based rare earth magnet (wherein R is a rare earth element) having excellent coercive force and a method for producing the same.

Background

An R-Fe-B rare earth magnet comprises a main phase and a grain boundary phase present around the main phase. The main phase is provided with R₂Fe₁₄A magnetic phase of crystal structure of type B. By this main phase, a high remanent magnetization is obtained.

Among R-Fe-B-based rare earth magnets, Nd-Fe-B-based rare earth magnets (hereinafter, sometimes referred to as "neodymium magnets") having an excellent balance between performance and price, and in which Nd is selected as R, are most common. Therefore, neodymium magnets have rapidly spread, and the amount of Nd used has increased dramatically, and in the future, the amount of Nd used may exceed the amount of Nd produced. Therefore, various attempts have been made to replace a part of Nd with light rare earth elements such as Ce, La, Y, and Sc.

For example, Japanese patent laid-open publication No. 2014-216339 discloses a (Nd, Ce) -Fe-B rare earth magnet in which a part of Nd in a main phase is substituted with Ce. The (Nd, Ce) -Fe-B-based rare earth magnet disclosed in Japanese patent application laid-open No. 2014-216339 is obtained by sintering magnetic powder having a main phase with a particle size of micrometer level at a high temperature (1000-1200 ℃) for a long time (8-50 hours). By this sintering at a high temperature for a long time, the main phase of the (Nd, Ce) -Fe-B-based rare earth magnet disclosed in japanese patent laid-open No. 2014-216339 has a core/shell structure, and the proportion of Nd present in the shell portion is increased as compared with that in the core portion.

Further, international publication No. 2014/196605 discloses a rare earth magnet produced by using an R-Fe-B-based rare earth magnet containing a light rare earth element as a precursor and diffusing and penetrating a modifier containing a rare earth element other than the light rare earth element into the precursor. Further, as a specific example, international publication No. 2014/196605 discloses a rare earth magnet produced by diffusing and infiltrating a melt of an Nd — Cu alloy as a modifier into a (Nd, Ce) -Fe — B-based rare earth magnet precursor.

In the specific example disclosed in international publication No. 2014/196605, by diffusion-infiltrating an Nd — Cu alloy as a modifier into a (Nd, Ce) -Fe — B-based rare earth magnet precursor, the main phase has a core/shell structure, and the proportion of Nd present in the shell portion is increased as compared with that in the core portion.

Further, the main phase of the rare earth magnet precursor used in the specific example disclosed in international publication No. 2014/196605 has been crystallized in a nano state. In addition, the rare earth magnet precursor is subjected to a thermoplastic processing in advance before the modifier is diffused and impregnated, thereby imparting anisotropy.

Disclosure of Invention

In the (Nd, Ce) -Fe-B-based rare earth magnet, if the main phase does not have a core/shell structure as in the (Nd, Ce) -Fe-B-based rare earth magnet disclosed in Japanese unexamined patent publication No. 2014-216339, the coercive force is lowered. This is because Ce₂Fe₁₄Anisotropy field ratio Nd of B₂Fe₁₄B has a small anisotropic magnetic field.

On the other hand, if the main phase is a core/shell structure as in the (Nd, Ce) -Fe-B rare earth magnet disclosed in international publication No. 2014/196605, and the proportion of Nd present in the shell portion is higher than in the core portion, the coercivity that is lowered by the inclusion of Ce can be compensated for. This is because, by increasing Nd in the shell section as compared with in the core section, and thereby increasing the anisotropic magnetic field in the shell section as compared with in the core section, it is possible to suppress the generation of nuclei of magnetization reversal of the surfaces of the main phase particles and the growth of nuclei from the adjacent main phase particles.

However, in an R-Fe-B-based rare earth magnet in which a part of Nd and/or Pr is replaced with a light rare earth element such as Ce, further improvement in coercive force is required.

Disclosed are a rare earth magnet having further improved coercive force in an R-Fe-B rare earth magnet in which a part of Nd and/or Pr is replaced with a light rare earth element such as Ce, and a method for producing the rare earth magnet.

The rare earth magnet and the method for manufacturing the same according to the present disclosure include the following aspects.

Aspects of the present invention relate to rare earth magnets. The above embodiment includes a main phase and a grain boundary phase existing around the main phase.

The overall composition in terms of molar ratio of the above scheme is represented by the formula (R)² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _v·(R³ _(1-p)M² _p)_q·(R⁴ _(1-s)M³ _s)_t(wherein, R¹Is one or more elements selected from Ce, La, Y and Sc, R²And R³Is more than one element selected from Nd and Pr⁴Is a rare earth element containing at least one element selected from Gd, Tb, Dy and Ho, M¹Is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In and Mn and inevitable impurity elements, M²Is a reaction with R³Alloying metal elements other than rare earth elements and inevitable impurity elements, M³Is a reaction with R⁴A metal element other than an alloyed rare earth element and an unavoidable impurity element, and 0.1 ≦ x ≦ 1.0, 12.0 ≦ y ≦ 20.0, 5.0 ≦ z ≦ 20.0, 0 ≦ w ≦ 8.0, 0 ≦ v ≦ 2.0, 0.05 ≦ p ≦ 0.40, 0.1 ≦ q ≦ 15.0, 0.05 ≦ s ≦ 0.40, and 0.1 ≦ t ≦ 5.0. ) And (4) showing.

The main phase of the above scheme has R₂Fe₁₄A B-type (wherein R is a rare earth element), the primary phase having an average particle diameter of 0.1 to 20 [ mu ] m and comprising a core portion, a first shell portion present around the core portion, and a second shell portion present around the first shell portion.

In the above aspect, the total molar ratio of Nd and Pr in the first shell portion is higher than the total molar ratio of Nd and Pr in the core portion, and the total molar ratio of Nd and Pr in the second shell portion is lower than the total molar ratio of Nd and Pr in the first shell portion.

The second shell portion of the above embodiment contains one or more elements selected from Gd, Tb, Dy, and Ho, the total molar ratio of Gd, Tb, Dy, and Ho in the second shell portion is higher than the total molar ratio of Gd, Tb, Dy, and Ho in the core portion, and the total molar ratio of Gd, Tb, Dy, and Ho in the second shell portion is higher than the total molar ratio of Gd, Tb, Dy, and Ho in the first shell portion.

In the above scheme, x may be 0.5 ≦ x ≦ 1.0.

In the above aspect, R is¹May be one or more elements selected from Ce and La, and R is as defined above²And the above R³Can be Nd, andand the above-mentioned R⁴May be one or more elements selected from Tb and Nd.

In the above aspect, the total of the molar ratios of Nd and Pr in the first shell portion may be 1.2 to 3.0 times the total of the molar ratios of Nd and Pr in the core portion,

the total molar ratio of Nd and Pr in the second shell may be 0.5 to 0.9 times the total molar ratio of Nd and Pr in the first shell.

The total molar ratio of Gd, Tb, Dy, and Ho in the second shell portion may be 2.0 times or more the total molar ratio of Gd, Tb, Dy, and Ho in the core portion, and the total molar ratio of Gd, Tb, Dy, and Ho in the second shell portion may be 2.0 times or more the total molar ratio of Gd, Tb, Dy, and Ho in the first shell portion.

The manufacturing method of the scheme comprises the following steps: preparing a first rare earth magnet precursor; preparing a first modified material; and diffusion-impregnating the first modification material into the first rare-earth magnet precursor.

The first rare earth magnet precursor has a main phase and a grain boundary phase present around the main phase, and the overall composition expressed by a molar ratio is represented by the formula (R)² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _v·(R³ _(1-p)M² _p)_q(wherein, R¹Is one or more elements selected from Ce, La, Y and Sc, R²And R³Is one or more elements selected from Nd and Pr, M¹Is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In and Mn and inevitable impurity elements, M²Is a reaction with R³A metal element other than an alloyed rare earth element and an unavoidable impurity element, and 0.1 ≦ x ≦ 1.0, 12.0 ≦ y ≦ 20.0, 5.0 ≦ z ≦ 20.0, 0 ≦ w ≦ 8.0, 0 ≦ v ≦ 2.0, 0.05 ≦ p ≦ 0.40, and 0.1 ≦ q ≦ 15.0. ) And (4) showing. In addition, the main phase has R₂Fe₁₄Crystal structure of B type (wherein R is rare earth element), average grain diameter of the above main phaseThe primary phase has a core part and a first shell part existing around the core part, and the total molar ratio of Nd and Pr in the first shell part is higher than the total molar ratio of Nd and Pr in the core part.

The first modified material has a formula R expressed by a molar ratio⁴ _(1-s)M³ _s(wherein, R⁴Is a rare earth element containing at least one element selected from Gd, Tb, Dy and Ho, M³Is a reaction with R⁴A metal element other than the alloyed rare earth element and an inevitable impurity element, and 0.05 s 0.40. ) The composition shown.

In the manufacturing method according to the above aspect, the method may further include: preparing a second rare earth magnet precursor; preparing a second modified material; and diffusing and infiltrating the second modifying material into the second rare-earth magnet precursor to obtain the first rare-earth magnet precursor.

The second rare earth magnet precursor has a main phase and a grain boundary phase present around the main phase, and the overall composition expressed by the molar ratio is represented by the formula (R)² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _v(wherein, R¹Is one or more elements selected from Ce, La, Y and Sc, R²Is one or more elements selected from Nd and Pr, M¹Is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In and Mn and an unavoidable impurity element, and 0.1 ≦ x ≦ 1.0, 12.0 ≦ y ≦ 20.0, 5.0 ≦ z ≦ 20.0, 0 ≦ w ≦ 8.0, and 0 ≦ v ≦ 2.0. ) The main phase has R₂Fe₁₄A crystal structure of type B (wherein R is a rare earth element), and the average grain diameter of the main phase is 0.1-20 μm.

The second modifying material has a formula R expressed by a molar ratio³ _(1-p)M² _p(wherein, R³Is one or more elements selected from Nd and Pr, M²Is a reaction with R³A metal element other than the alloyed rare earth element and an inevitable impurity element, and 0.05 ≦ p ≦ 0.40. )The composition shown.

In the manufacturing method according to the above aspect, the method may further include: preparing a second rare earth magnet precursor powder; preparing a second modified material powder; and mixing and sintering the second rare earth magnet precursor powder and the second modifying material powder to obtain the first rare earth magnet precursor.

The second rare earth magnet precursor powder has a main phase and a grain boundary phase present around the main phase, and the overall composition expressed by the molar ratio is represented by the formula (R)² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _v(wherein, R¹Is one or more elements selected from Ce, La, Y and Sc, R²Is one or more elements selected from Nd and Pr, M¹Is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In and Mn and an unavoidable impurity element, and 0.1 ≦ x ≦ 1.0, 12.0 ≦ y ≦ 20.0, 5.0 ≦ z ≦ 20.0, 0 ≦ w ≦ 8.0, and 0 ≦ v ≦ 2.0. ) The main phase has R₂Fe₁₄A crystal structure of type B (wherein R is a rare earth element), and the average grain diameter of the main phase is 0.1-20 μm.

The second modifier powder has the formula R expressed by a molar ratio³ _(1-p)M² _p(wherein, R³Is one or more elements selected from Nd and Pr, M²Is a reaction with R³A metal element other than the alloyed rare earth element and an inevitable impurity element, and 0.05 < p < 0.40. ) The composition shown.

In the manufacturing method according to the above aspect, the first modifier powder may have a diffusion permeation temperature lower than a diffusion permeation temperature of the second modifier powder or the second modifier material.

In the production method of the above aspect, x may be 0.5 ≦ x ≦ 1.0.

In the production method of the above aspect, R is¹May be one or more elements selected from Ce and La, and R is as defined above²And the above R³Can be Nd, and the above R⁴May be selected from TbAnd Nd.

According to the present disclosure, a rare earth magnet having further improved coercive force can be provided by providing a core portion in which a part of Nd or the like is substituted with a light rare earth element such as Ce, a first shell portion having a high content ratio of Nd or the like, and a second shell portion having a high presence ratio of a heavy rare earth element such as Tb. Further, according to the present disclosure, a method for producing a rare earth magnet having further improved coercive force can be provided by diffusing and infiltrating a heavy rare earth element into a rare earth magnet precursor having a main phase including a core portion in which a part of Nd or the like is substituted with a light rare earth element and a first shell portion having a high content ratio of Nd or the like.

Drawings

Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, wherein like reference numerals represent like elements, and wherein:

fig. 1A is a cross-sectional explanatory view schematically showing a state in which a rare earth magnet precursor having a main phase without a core/shell structure is provided by bringing a modifying material containing a medium rare earth element into contact to replace a part of Nd and/or Pr with a light rare earth element.

Fig. 1B is a cross-sectional explanatory view schematically showing a state of diffusion and permeation of the medium rare earth element after heating in the state of fig. 1A.

Fig. 1C is a cross-sectional explanatory view schematically showing a state where a heavy rare earth element-containing modification material is brought into contact with the rare earth magnet precursor shown in fig. 1B.

Fig. 1D is a cross-sectional explanatory view schematically showing a state of diffusion permeation of the heavy rare earth element after heating in the state of fig. 1C.

Fig. 2 is an explanatory view schematically showing the structure of the rare earth magnet of the present disclosure.

FIG. 3A is a graph showing the results of tissue observation using STEM-EDX for the sample of example 1.

Fig. 3B is a graph showing the results of surface analysis of Tb using STEM-EDX for the site shown in fig. 3A.

FIG. 3C is a graph showing the results of surface analysis of Ce using STEM-EDX for the sites shown in FIG. 3A.

FIG. 3D is a graph showing the results of surface analysis of La using STEM-EDX for the region shown in FIG. 3A.

Fig. 3E is a view showing the result of surface analysis of Nd using STEM-EDX for the portion shown in fig. 3A.

Fig. 4A is a high-resolution STEM image showing the crystal structure of the < 110 > incident direction of the core portion with respect to the sample of example 1.

Fig. 4B is a high-resolution STEM image showing the crystal structure in the < 110 > incident direction of the first shell portion for the sample of example 1.

Fig. 4C is a high-resolution STEM image showing the crystal structure in the < 110 > incident direction of the second shell portion for the sample of example 1.

FIG. 5 is a graph showing the results of line analysis in the direction of the arrow shown in FIG. 3E using STEM-EDX for the sample of example 1.

FIG. 6A is a view showing the results of tissue observation using SEM-EDX for the sample of comparative example 1.

Fig. 6B is a graph showing the results of surface analysis of Tb using SEM-EDX for the sites shown in fig. 6A.

Fig. 6C is a graph showing the results of surface analysis of Ce using SEM-EDX for the sites shown in fig. 6A.

Fig. 6D is a view showing the result of surface analysis of Nd using SEM-EDX for the portion shown in fig. 6A.

Fig. 7A is a cross-sectional explanatory view schematically showing a state in which a rare earth magnet precursor having a main phase without a core/shell structure is provided by bringing a modifying material containing a heavy rare earth element into contact to replace a part of Nd and/or Pr with a light rare earth element.

Fig. 7B is a cross-sectional explanatory view schematically showing a diffusion permeation state of the heavy rare earth element after heating in the state shown in fig. 7A.

Detailed Description

Embodiments of the rare earth magnet and the method for manufacturing the same according to the present disclosure will be described in detail below. The embodiments described below do not limit the rare earth magnet and the method for manufacturing the same according to the present disclosure.

When the coercive force is to be increased, it is effective to increase the anisotropic magnetic field of the main phase. In addition, when the anisotropic magnetic field of the main phase is to be increased, it is effective to contain a heavy rare earth element in the main phase. The method of making the main phase contain a heavy rare earth element will be described with reference to the drawings.

Fig. 7A is a cross-sectional explanatory view schematically showing a state in which a rare earth magnet precursor having a main phase without a core/shell structure is provided by bringing a modifying material containing a heavy rare earth element into contact to replace a part of Nd and/or Pr with a light rare earth element. Fig. 7B is a cross-sectional explanatory view schematically showing a diffusion permeation state of the heavy rare earth element after heating in the state shown in fig. 7A.

As shown in fig. 7A, the non-core/shell rare earth magnet precursor 100 is brought into contact with the heavy rare earth element-modifying material 300. The non-core/shell rare earth magnet precursor 100 is a rare earth magnet precursor in which a part of Nd and/or Pr is substituted with a light rare earth element and which has a main phase having no core/shell structure. The heavy rare earth element-modified material 300 is a modified material containing a heavy rare earth element. The non-core/shell rare earth magnet precursor 100 has a main phase 10 and a grain boundary phase 50.

If the non-core/shell rare earth magnet precursor 100 and the heavy rare earth element-modified material 300 are heated in the state shown in fig. 7A, the main phase 10 in the vicinity of the surface layer portion of the non-core/shell rare earth magnet precursor 100 becomes the coarsened main phase 70 as shown in fig. 7B. Without being bound by theory, the melting point of the main phase 10 is lowered because a portion of Nd and/or Pr is replaced by the light rare earth element in the non-core/shell rare earth magnet precursor 100. Therefore, it is considered that the heavy rare earth element in the heavy rare earth element-modified material 300 is likely to react with the heavy rare earth element during heating, and most of the heavy rare earth element in the heavy rare earth element-modified material 300 is taken up in the main phase 10 near the surface layer portion to become the coarsened main phase 70. As a result, the heavy rare earth element in the heavy rare earth element-modified material 300 does not reach the inside of the non-core/shell rare earth magnet precursor 100, and the coercive force is not increased.

For example, if the main phase 10 is (Ce, La, Nd)₂Fe₁₄B, the heavy rare earth element-modified material 300 is a Tb-Ga alloy, and the surface layer portion thereof isThe primary phase 10 of (D) reacts with Tb to form (Ce, La, Nd, Tb) as a coarsened primary phase 70₂Fe₁₄B. Further, Tb in the heavy rare earth element-modified material 300 does not reach the inside of the non-core/shell rare earth magnet precursor 100, and the coercive force is not improved.

The heavy rare earth element in the heavy rare earth element-modified material 300 is allowed to penetrate to the inside of the non-core/shell rare earth magnet precursor 100, as described below. This will be described with reference to the drawings.

Fig. 1A is a cross-sectional explanatory view schematically showing a state in which a rare earth magnet precursor having a main phase without a core/shell structure is provided by bringing a modifying material containing a medium rare earth element into contact to replace a part of Nd and/or Pr with a light rare earth element. Fig. 1B is a cross-sectional explanatory view schematically showing a state of diffusion and permeation of the medium rare earth element after heating in the state of fig. 1A. Fig. 1C is a cross-sectional explanatory view schematically showing a state where a heavy rare earth element-containing modification material is brought into contact with the rare earth magnet precursor shown in fig. 1B. Fig. 1D is a cross-sectional explanatory view schematically showing a state of diffusion permeation of the heavy rare earth element after heating in the state of fig. 1C.

As shown in fig. 1A, a non-core/shell rare earth magnet precursor 100 is brought into contact with a medium rare earth element-modifying material 200. The non-core/shell rare earth magnet precursor 100 is a rare earth magnet precursor in which a part of Nd and/or Pr is substituted with a light rare earth element and which has a main phase having no core/shell structure. The medium rare earth element modified material 200 is a modified material containing a medium rare earth element. The non-core/shell rare earth magnet precursor 100 has a main phase 10 and a grain boundary phase 50. The medium rare earth elements are Nd and Pr.

If the non-core/shell rare-earth magnet precursor 100 and the medium rare-earth element-modified material 200 are heated in the state shown in fig. 1A, the melt of the medium rare-earth element-modified material 200 diffuses and permeates through the grain boundary phase 50 as shown in fig. 1B. Further, a part of the middle rare earth element in the melt of the middle rare earth element-modifying material 200 diffused and infiltrated into the grain boundary phase 50 is substituted with a part of the light rare earth element in the vicinity of the surface layer portion of the main phase 10, thereby forming the first shell portion 30. The first shell portion 30 is formed in the vicinity of a surface layer portion of the primary phase 10, and the core portion 20 is formed in the region of the primary phase 10 other than the first shell portion 30. Also, the first shell portion 30 has a higher proportion of the medium rare earth element than the core portion 20.

Without being bound by theory, the reason for forming the core portion 20 and the first shell portion 30 in the case where the rare earth element-modified material is used, unlike the case where the heavy rare earth element-modified material is used, is considered as follows. As described above, the non-core/shell rare earth magnet precursor 100 has a portion of Nd and/or Pr replaced with a light rare earth element, so that the melting point of the main phase 10 is lowered. However, the reactivity of the medium rare earth element in the medium rare earth element-modified material 200 with the main phase 10 is low as compared with the heavy rare earth element in the heavy rare earth element-modified material 300. Therefore, a part of the middle rare earth element in the middle rare earth element-modified material 200 is substituted with a part of the light rare earth element in the vicinity of the surface layer portion of the main phase 10. Furthermore, the melt of the medium rare earth element-modifying material reaches the inside of the non-core/shell rare earth magnet precursor 100, and the primary phase 10 in the inside of the non-core/shell rare earth magnet precursor 100 also forms the first shell portion.

Then, as shown in fig. 1C, the heavy rare earth element-modifying material 300 is brought into contact with a rare earth magnet precursor (hereinafter sometimes referred to as "core/shell rare earth magnet precursor 150") provided with the primary phase 10 having the core portion 20 and the first shell portion 30, and heated. Then, as shown in fig. 1D, the melt of the heavy rare-earth element modification material 300 diffuses and permeates through the grain boundary phase 50. Further, a portion of the heavy rare earth element in the melt of the heavy rare earth element-modifying material 300 diffused and infiltrated into the grain boundary phase 50 is replaced with a portion of the light rare earth element and a portion of the medium rare earth element in the first shell portion 30, forming the second shell portion 40. The second shell portion 40 is formed near a surface layer portion of the first shell portion 30. Also, the second shell portion 40 has a lower proportion of the medium rare earth element than the first shell portion 30, and the second shell portion 40 contains the heavy rare earth element.

Without being bound by theory, the reason for forming the second shell portion 40 is believed to be as follows. As shown in FIG. 1C, the first shell portion 30 contacts the grain boundary phase 50 before the diffusion penetration of the melt of the heavy rare earth element-modifying material 300. Also, as described above, the proportion of the rare earth element present in the first shell portion 30 is higher than the proportion of the rare earth element present in the core portion 20. Therefore, when the solution of the heavy rare earth element modification material 300 that has been diffused and permeated passes through the grain boundary phase 50, the solution does not excessively react with the first shell portion 30. Further, a part of the light rare earth element and a part of the medium rare earth element in the vicinity of the surface layer portion of the first shell portion 30 are substituted with the heavy rare earth element in the melt of the heavy rare earth element-modified material 300.

In this way, as shown in fig. 1D, up to the main phase 10 inside the rare earth magnet 500 of the present disclosure, the second shell portion 40 containing a heavy rare earth element is formed. If the main phase 10 contains a heavy rare earth element, the anisotropic magnetic field of the main phase 10 increases, and therefore the coercive force of the entire rare earth magnet 500 of the present disclosure increases. In addition, as shown in fig. 1D, since the second shell portion 40 in which a heavy rare earth element is present is formed in the outermost shell portion of the main phase 10, it is difficult for nucleation on the particle surface of the main phase 10 and nucleation growth from the particles of the adjacent main phase 10 to occur, contributing to improvement of the coercive force.

Next, technical features of the rare earth magnet and the method for manufacturing the same according to the present disclosure will be explained.

Rare earth magnet

First, technical features of the rare earth magnet of the present disclosure will be explained.

Fig. 2 is an explanatory view schematically showing the structure of the rare earth magnet of the present disclosure. As shown in fig. 2, the rare earth magnet 500 of the present disclosure is provided with a main phase 10 and a grain boundary phase 50. The primary phase 10 includes a core portion 20, a first shell portion 30, and a second shell portion 40. The overall composition, main phase 10, and grain boundary phase 50 of the rare earth magnet 500 of the present disclosure are explained below. In addition, the core section 20, the first shell section 30, and the second shell section 40 will be described with respect to the primary phase 10.

Integral assembly

The overall composition of the rare earth magnet 500 of the present disclosure is explained. The overall composition of the rare earth magnet 500 of the present disclosure is a composition in which all of the main phase 10 and the grain boundary phase 50 are combined.

The overall composition of the rare earth magnet expressed by the molar ratio of the present disclosure is represented by formula(R² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _v·(R³ _(1-p)M² _p)_q·(R⁴ _(1-s)M³ _s)_tAnd (4) showing. In the formula, (R)² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _v·(R³ _(1-p)M² _p)_qDenotes the composition from the first rare earth magnet precursor. (R)⁴ _(1-s)M³ _s)_tDenotes the composition from the first modifying material.

The rare earth magnet of the present disclosure has the formula (R)⁴ _(1-s)M³ _s)_tA first modified material having the composition represented by the formula (R)² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _v·(R³ _(1-p)M² _p)_qThe inside of the first rare earth magnet precursor of the composition shown. The first rare earth magnet precursor is an example of a rare earth magnet precursor (core/shell rare earth magnet precursor 150) having a primary phase 10 having a core portion 20 and a first shell portion 30, shown in fig. 1C. The first modified material is an example of the modified material containing a heavy rare earth element (heavy rare earth element-modified material 300) shown in fig. 1C.

Composition formula (R) from a first rare earth magnet precursor² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _v·(R³ _(1-p)M² _p)_qIn (R)² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _vFrom a second rare earth magnet precursor, (R)³ _(1-p)M² _p)_qFrom the second modifying material.

The first rare earth magnet precursor is prepared by reacting a compound having the formula (R)³ _(1-p)M² _p)_qThe second modifying material of the composition represented by (R) is diffusion-impregnated into the composition having the formula² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _vThe inside of the second rare earth magnet precursor of the composition shown. The second rare earth magnet precursor is an example of the non-core/shell rare earth magnet precursor 100 shown in fig. 1A. The second modified material is an example of the medium rare earth element-modified material 200 shown in fig. 1A.

If q parts by mole of the second modification material are diffused and impregnated into 100 parts by mole of the second rare earth magnet precursor, then (100+ q) parts by mole of the first rare earth magnet precursor are obtained. Further, if t molar parts of the first modification material is diffused to penetrate inside (100+ q) molar parts of the first rare earth magnet precursor, a (100+ q + t) molar part of the rare earth magnet of the present disclosure is obtained.

In the formula representing the entire composition of the rare earth magnet of the present disclosure, R¹And R²Is y mole fraction, Fe is (100-y-w-z-v), Co is w mole fraction, B is z mole fraction, and M is¹In v parts, so that they add up to y parts by mole + (100-y-w-z-v) parts by mole + w parts by mole + z parts by mole + v parts by mole 100 parts by mole. R³And M²Q parts by mole. R⁴And M³The total of (a) and (b) is t mole parts.

In the above formula, it means that in R² _(1-x)R¹ _xIn relation to R²And R¹In a molar ratio, R of (1-x) is present²R in the presence of x¹. Similarly, in the above formula, it means that R is³ _(1-p)M² _pIn relation to R³And M²In a molar ratio, R of (1-p) is present³M in the presence of p². In addition, similarly, in the above formula, it means that R is⁴ _(1-s)M³ _sIn relation to R⁴And M³In total of (1)The molar ratio indicates the presence of R of (1-s)⁴M in the presence of s³。

In the above formula, R¹Is one or more elements selected from Ce, La, Y and Sc. Ce is cerium, La is lanthanum, Y is yttrium, and Sc is scandium. R²And R³Is one or more elements selected from Nd and Pr. Nd is neodymium and Pr is praseodymium. R⁴Is a rare earth element containing at least one element selected from Gd, Tb, Dy and Ho, Gd is gadolinium, Tb is terbium, Dy is dysprosium, and Ho is holmium. Fe is iron. Co is cobalt. B is boron. M¹Is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In and Mn, and inevitable impurity elements. Ga is gallium, Al is aluminum, Cu is copper, Au is gold, Ag is silver, Zn is zinc, In is indium, and Mn is manganese. M²Is a reaction with R³Metal elements other than alloyed rare earth elements and inevitable impurity elements. M³Is a reaction with R⁴Metal elements other than alloyed rare earth elements and inevitable impurity elements.

In the present specification, the rare earth elements include 17 elements of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu unless otherwise specified. Wherein Sc, Y, La and Ce are light rare earth elements unless otherwise specified. In addition, Pr, Nd, Pm, Sm and Eu are medium rare earth elements unless otherwise specified. Incidentally, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu are heavy rare earth elements unless otherwise specified. In general, the rare earth element is highly rare, and the rare earth element is low. The rarity of the medium rare earth elements is between the heavy rare earth elements and the light rare earth elements.

The following describes the constituent elements of the rare earth magnet of the present disclosure represented by the above formula.

R¹

R¹Is a necessary component for the rare earth magnet of the present disclosure. As mentioned above, R¹Is more than one element selected from Ce, La, Y and Sc, and belongs to light rare earth elements. R¹Is a main phase (R)₂Fe₁₄Phase B). By adding R near the surface layer part of the main phase¹At least a part of the second modifying material is R³The primary phase can thereby have a core portion and a first shell portion. From the viewpoint of substitution, R¹Preferably one or more elements selected from Ce and La.

R²

As mentioned above, R²Is more than one element selected from Nd and Pr, and belongs to the medium rare earth elements. R²Is a main phase (R)₂Fe₁₄Phase B). In the rare earth magnet of the present disclosure, from the viewpoint of balance between performance and price, it is preferable to increase the content of Nd and Pr, and it is more preferable to increase the content of Nd. As R²In the case where Nd and Pr coexist, didymium may be used. From the performance point of view, R²Nd is preferred.

R¹And R²In a molar ratio of

In the rare earth magnet of the present disclosure, R¹And R²Is an element from the second rare earth magnet precursor. Relative to R¹And R²In a molar ratio, R in the presence of x¹In the presence of R of (1-x)². Further, x ≦ 1.0 is satisfied.

As shown in fig. 1A, by the presence of R near the surface layer portion of the main phase 10¹R with second modifying Material 200³Replacing to form the first shell portion 30, so R¹Even in small amounts, must be present. As long as x is 0.1 or more, the formation of the first shell portion 30 is enabled to be substantially recognized. From the viewpoint of formation of the first shell portion 30, x may be 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, or 1.0. By x is 1.0, it is meant relative to R¹(light rare earth element) and R²(Nd and/or Pr) are all R¹(light rare earth elements).

At R₂Fe₁₄In the B phase (main phase), R is higher in the anisotropic magnetic field (coercive force) and residual magnetization when a rare earth element other than the light rare earth element is contained in a larger amount than the light rare earth element. By diffusion-impregnating a second modifying material into a second rare earth magnet precursorAnd R of the rare earth magnet precursor is formed near the surface layer portion of the main phase 10¹R of a part of (light rare earth element) modifying material³(Nd and/or Pr) to form the first shell portion 30. This increases the content ratio of Nd and/or Pr (rare earth elements other than the light rare earth element) in the main phase 10, and thus contributes to an improvement in the anisotropic magnetic field (coercive force) and residual magnetization.

When the anisotropic magnetic field (coercive force) and residual magnetization of the outer periphery of the main phase 10 are increased, the anisotropic magnetic field (coercive force) and residual magnetic field of the entire rare earth magnet can be efficiently increased. Therefore, R is put in the first shell portion 30¹R for (light rare earth elements)³(Nd and/or Pr) substitution is preferable in terms of improvement in coercive force.

R¹And R²In total content ratio of

In the above formula, R¹And R²The total content of (b) is represented by y, and satisfies 12.0 ≦ y ≦ 20.0. The value of y is a content ratio of the second rare earth magnet precursor, and corresponds to atomic%.

When y is 12.0 or more, the α Fe phase does not exist in a large amount in the second rare earth magnet precursor, and a sufficient amount of the main phase (R) can be obtained₂Fe₁₄Phase B). From this viewpoint, y may be 12.4 or more, 12.8 or more, or 13.2 or more. On the other hand, if y is 20.0 or less, the grain boundary phase does not become excessive. From this viewpoint, y may be 19.0 or less, 18.0 or less, or 17.0 or less.

B

B constitutes the main phase 10 (R) as shown in FIG. 2₂Fe₁₄Phase B), which affects the existence ratio of the main phase 10 and the grain boundary phase 50.

The content ratio of B is represented by z in the above formula. The value of z is a content ratio relative to the second rare earth magnet precursor, corresponding to atomic%. When z is 20.0 or less, a rare earth magnet in which the main phase 10 and the grain boundary phase 50 are suitably present can be obtained. From this viewpoint, z may be 18.0 or less, 16.0 or less, 14.0 or less, 12.0 or less, 10.0 or less, or 8.0 or less. On the other hand, if z is 5.0 or more, it is difficult to occur: utensil for cleaning buttockHas Th₂Zn₁₇And/or Th₂Ni₁₇The phase of crystal structure of form (III) is generated in large quantity, as a result R₂Fe₁₄The formation of the B phase is less hindered. From this viewpoint, z may be 5.8 or more, 6.0 or more, 6.2 or more, 6.4 or more, 6.6 or more, 6.8 or more, or 7.0 or more.

Co

Co is an element that can be substituted with Fe in the main phase and grain boundary phase. In the present specification, the term "Fe" means that a part of Fe is replaced with Co. For example, R is₂Fe₁₄Part of Fe in B phase is replaced by Co to form R₂(Fe、Co)₁₄And (B) phase.

By replacing a part of Fe with Co, R₂Fe₁₄Phase B is R₂(Fe、Co)₁₄Phase B, thereby increasing the curie point of the rare earth magnet of the present disclosure. In the case where the increase in Curie point is not desired, Co may be absent, and the presence of Co is not essential.

In the above formula, the content ratio of Co is represented by w. The value of w is a content ratio relative to the second rare earth magnet precursor, corresponding to atomic%. If w is 0.5 or more, the Curie point is substantially improved. From the viewpoint of improving the curie point, w may be 1.0 or more, 2.0 or more, 3.0 or more, or 4.0 or more. On the other hand, since Co is expensive, w may be 8.0 or less, 7.0 or less, or 6.0 or less from the economical viewpoint.

M¹

Is about M¹In other words, the rare earth magnet can be contained in a range that does not impair the characteristics of the rare earth magnet of the present disclosure. At M¹May contain inevitable impurity elements. In the present specification, the inevitable impurity element means an impurity element contained in a raw material of the rare earth magnet, an impurity element mixed in a production process, or the like, which is inevitably contained or causes a significant increase in production cost in order to avoid the impurity element. The impurity elements and the like mixed in the production process include elements contained in a range that does not affect the magnetic properties due to convenience in production. In addition, R is contained as an inevitable impurity element¹And R²Rare earth elements other than the selected rare earth elements are inevitably mixed for the above-described reasons.

Examples of the element that can be contained within a range that does not impair the effects of the rare earth magnet and the method for producing the same of the present disclosure include Ga, Al, Cu, Au, Ag, Zn, In, and Mn. These elements are only in M¹Is present below the upper limit of the content of (a), these elements do not substantially affect the magnetic properties. Therefore, these elements can be treated equally as inevitable impurity elements. In addition to these elements, M is defined as¹And may contain inevitable impurity elements.

In the above formula, M¹The content ratio of (B) is represented by v. The value of v is a content ratio with respect to the second rare earth magnet precursor, corresponding to atomic%. If the value of v is 2.0 or less, the magnetic characteristics of the rare earth magnet of the present disclosure are not impaired. From this viewpoint, v may be 1.5 or less, 1.0 or less, or 0.5 or less.

As M¹Since Ga, Al, Cu, Au, Ag, Zn, In, Mn, and inevitable impurity elements cannot be made to be present, the lower limit of v is not practically problematic even if it is 0.05, 0.1, or 0.2.

Fe

Fe is R explained so far¹、R²Co, B and M¹The balance of (b), the Fe content ratio is represented by (100-y-w-z-v). When y, w, z and v are in the ranges described so far, the main phase 10 and the grain boundary phase 50 are obtained as shown in FIG. 2.

R³

R³Is an element from the second modifying material. As shown in fig. 1A, the second modification material 200 is diffusion-impregnated into the inside of the second rare-earth magnet precursor 100. R in the vicinity of the surface layer portion of the main phase 10¹With R of the second modified material 200³And replacing to form the first shell portion 30.

R³Is more than one element selected from Nd and Pr, and belongs to the medium rare earth elements. Among the medium rare earth elements, Nd and Pr readily form R₂Fe₁₄And (B) phase. As aboveR of the main phase 10¹R of the second modifier 200 is applied to a part of the vicinity of the surface layer portion of the (light rare earth element)³(Nd and/or Pr) substitution increases the proportion of Nd and/or Pr present in the first shell portion 30. As a result, as described above, the heavy rare earth element is diffused and impregnated after the first shell portion 30 is formed, so that the heavy rare earth element is distributed in the rare earth magnet, thereby contributing to improvement of coercive force. In addition, in the first shell portion 30 present in the outer peripheral portion of the main phase 10, the presence ratio of Nd and/or Pr is increased, and therefore contributes to an increase in the anisotropic magnetic field (coercive force) and residual magnetization of the rare earth magnet of the present disclosure. From anisotropic magnetic field (coercive force) and remanent magnetization and from R¹(light rare earth element) as R from the viewpoint of replaceability³Nd is preferred.

M²

M²Is a reaction with R³Metal elements other than alloyed rare earth elements and inevitable impurity elements. Typically, M²To make R³ _(1-p)M² _pHas a melting point lower than R³Alloying elements and inevitable impurity elements. As M²Examples thereof include one or more elements selected from Cu, Al, Co and Fe, and inevitable impurity elements. As M²Preferably, at least one element selected from Cu, Al and Fe. From lowering R³ _(1-p)M² _pFrom the viewpoint of melting point of (A), M is²Particularly, Cu is preferable. The inevitable impurity element means an impurity element contained in a raw material, an impurity element mixed in a production process, or the like, which is inevitably contained or causes a significant increase in production cost in order to avoid the impurity element. The impurity elements and the like mixed in the production process include elements contained in a range that does not affect the magnetic properties due to convenience in production. In addition, R is contained as an inevitable impurity element³Rare earth elements other than the selected rare earth elements are inevitably mixed for the above-described reasons.

R³And M²Mole ofRatio of

R³And M²Form a compound having the formula R³ _(1-p)M² _pThe second modifier contains the alloy having the composition expressed by the molar ratio. Also, p satisfies 0.05 ≦ p ≦ 0.40.

If p is 0.05 or more, the melt of the second modification material 200 can be diffusion-infiltrated into the interior of the second rare-earth magnet precursor 100 at a temperature at which coarsening of the main phase 10 of the second rare-earth magnet precursor 100 shown in fig. 1A can be avoided. From this viewpoint, p is preferably 0.07 or more, and more preferably 0.10 or more. On the other hand, if p is 0.40 or less, M remaining in the grain boundary phase 50 of the rare earth magnet 500 of the present disclosure is suppressed after the second modification material 200 is diffusion-infiltrated into the second rare earth magnet precursor 100²In the above range, the decrease in residual magnetization can be suppressed. From this viewpoint, p may be 0.35 or less, 0.30 or less, 0.25 or less, 0.20 or less, or 0.15 or less.

R⁴

R⁴Is an element from the first modifying material. As shown in fig. 1C and 1D, the melt of the first modification material 300 is diffusion-impregnated into the interior of the first rare-earth magnet precursor 150. Part of the light rare earth element and part of Nd and/or Pr near the surface layer part of the first shell part 30 are expressed by R of the first modified material 300⁴And replacing to form the second shell portion 40.

R⁴Is a rare earth element containing at least one or more elements selected from Gd, Tb, Dy and Ho. Namely, R⁴Is a rare earth element containing one or more heavy rare earth elements selected from Gd, Tb, Dy and Ho. As described above, a portion of the light rare earth element and a portion of Nd and/or Pr near the surface layer portion of the first shell portion 30 shown in FIG. 1C are used with R of the first modified material 300⁴The second shell portion 40 is formed by substitution of the heavy rare earth element. From the viewpoint of substitution, R is⁴Preferably Tb. As shown in fig. 1D and 2, the second shell portion 40 containing a heavy rare earth element is also formed in the main phase 10 inside the rare earth magnet 500 of the present disclosure, and therefore the coercive force of the rare earth magnet 500 of the present disclosure as a whole is improved. In addition, as in FIG. 1DAs shown, since the second shell portion 40 in which a heavy rare earth element is present is formed in the outermost shell portion of the main phase 10, it is possible to suppress the generation of nuclei for magnetization reversal on the particle surface of the main phase 10 and the growth of nuclei from particles of the adjacent main phase 10, and therefore it is preferable for improvement of the coercive force.

M³

M³Is a reaction with R⁴Metal elements other than alloyed rare earth elements and inevitable impurity elements. Typically, M³To make R⁴ _(1-s)M³ _sHas a melting point lower than R⁴Alloying elements and inevitable impurity elements. As M³Examples thereof include at least one element selected from Ga, Cu, Al, Co and Fe, and inevitable impurity elements. R⁴Containing heavy rare earths, the melting point of which is high, thus lowering R⁴ _(1-s)M³ _sFrom the viewpoint of melting point of (A), M is³Ga and Cu are preferred. The inevitable impurity element is an impurity element which is inevitably contained in a raw material, an impurity element mixed in a production process, or the like, or which causes a significant increase in production cost in order to avoid the impurity element. The impurity elements and the like mixed in the production process include elements contained in a range that does not affect the magnetic properties due to convenience in production. In addition, R is contained as an inevitable impurity element⁴Rare earth elements other than the selected rare earth elements are inevitably mixed for the above-described reasons.

R⁴And M³In a molar ratio of

R⁴And M³Form a compound having the formula R⁴ _(1-s)M³ _sThe first modified material contains the alloy having the composition expressed by the molar ratio. And s satisfies 0.05 ≦ s ≦ 0.40.

If s is 0.05 or more, coarsening of the primary phase 10 of the first rare earth magnet precursor 150 shown in 1C can be avoided, and the second shell portion 30 can be made to react with the first modification material 300 at a temperature at which there is no excess reactionA melt of the modification material 300 is diffusion-impregnated into the interior of the first rare-earth magnet precursor 150. From this viewpoint, "s" is preferably 0.07 or more, more preferably 0.09 or more, and still more preferably 0.12 or more. On the other hand, if s is 0.40 or less, after the first modification material 300 is diffused and infiltrated into the first rare earth magnet precursor 150, M remaining in the grain boundary phase 50 of the rare earth magnet 500 of the present disclosure is suppressed³In the above range, the decrease in residual magnetization can be suppressed. From this viewpoint, s may be 0.35 or less, 0.30 or less, 0.25 or less, 0.20 or less, or 0.15 or less.

Molar ratio of element derived from rare earth magnet precursor to element derived from modifying material

In the above formula, the proportion of the second modification material to 100 molar parts of the second rare-earth magnet precursor is q molar parts. In addition, the proportion of the first modified material with respect to 100 molar parts of the second rare-earth magnet precursor is t molar parts. That is, if q parts by mole of the second modifier are diffused and impregnated into 100 parts by mole of the second rare-earth magnet precursor, 100 parts by mole + q parts by mole of the first rare-earth magnet precursor are obtained. Further, if t parts by mole of the first modification material is diffused and impregnated into 100 parts by mole + q parts by mole of the first rare earth magnet precursor, the rare earth magnet of the present disclosure becomes 100 parts by mole + q parts by mole + t parts by mole. Therefore, q is a molar ratio of the content of the element derived from the second modifier to the total content of the elements derived from the second rare-earth magnet precursor of 100. t is a molar ratio of the content of the element derived from the first modifier to the total content of the elements derived from the second rare-earth magnet precursor of 100. In other words, the rare earth magnet of the present disclosure is (100+ q + t) atomic% with respect to 100 atomic% of the second rare earth magnet precursor.

If q is 0.1 or more, R of the second modifier 200 can be used³(Nd and/or Pr) R of the main phase 10 of the second rare earth magnet precursor 100¹At least a portion of the (light rare earth element) is substituted, and the first shell portion 30 can be formed. By diffusing and infiltrating the heavy rare earth element after the formation of the first shell portion 30, the heavy rare earth element can be diffused into the interior of the rare earth magnet 500 of the present disclosure. In addition, the outer periphery of the main phase 10 is increasedNd and/or Pr are present in a ratio such that the anisotropy field (coercive force) and residual magnetization of the rare earth magnet 500 of the present disclosure can be improved. From these viewpoints, q may be 0.5 or more, 1.0 or more, 1.5 or more, 2.0 or more, 2.5 or more, 3.0 or more, 3.5 or more, 4.0 or more, 4.5 or more, 4.7 or more, 5.0 or more, or 5.5 or more. On the other hand, if q is 15.0 or less, M remaining in the grain boundary phase 50 of the rare earth magnet 500 of the present disclosure is suppressed²In the amount of (b) contributes to an increase in residual magnetization. From this viewpoint, q may be 14.0 or less, 13.0 or less, 12.0 or less, 11.0 or less, 10.4 or less, 10.0 or less, 9.5 or less, 9.0 or less, 8.5 or less, 8.0 or less, 7.5 or less, 7.0 or less, or 6.5 or less.

When t is 0.1 or more, the second shell portion 40 containing a heavy rare earth element is formed in the main phase 10, and the anisotropic magnetic field of the main phase 10 is increased, whereby the coercive force can be increased. From this viewpoint, t may be 0.2 or more, 0.4 or more, 0.6 or more, 0.8 or more, 1.0 or more, 1.2 or more, 1.4 or more, 1.5 or more, or 2.0 or more. On the other hand, even a relatively small amount of the heavy rare earth element can provide an effect of improving the anisotropic magnetic field generated by the heavy rare earth element, and the rare property of the heavy rare earth element is high. From these viewpoints, t may be 5.0 or less, 4.5 or less, 4.0 or less, 3.5 or less, 3.0 or less, or 2.5 or less.

As shown in fig. 2, the rare earth magnet 500 of the present disclosure is provided with a main phase 10 and a grain boundary phase 50. The primary phase 10 includes a core portion 20, a first shell portion 30, and a second shell portion 40. The main phase 10 and the grain boundary phase 50 will be described below. In addition, the core section 20, the first shell section 30, and the second shell section 40 will be described with respect to the primary phase 10.

Main phase

The main phase has R₂Fe₁₄Crystal structure of form B. R is rare earth element. Is referred to as R₂Fe₁₄The reason for the "B" form is that elements other than R, Fe and B may be contained in the main phase (in the crystal structure) in a substitution form and/or an invasion form. For example, in the main phase, a part of Fe may be replaced with Co. Alternatively, for example, in the main phase, a part of any one of elements R, Fe and B may be used as M¹And (4) replacement. OrE.g. in the main phase, M¹May be present in an invasive form.

The effect of the present invention, particularly the effect of forming the first shell portion and the second shell portion in the main phase to increase the coercive force, is obtained by providing the main phase 10 having a particle diameter of a micrometer level, for example, a sintered magnet, or a magnet having a nanocrystalline main phase, for example, a thermoplastic processed magnet.

The main phase has an average particle diameter of 0.1 to 20 μm. If the average particle diameter of the main phase is 0.1 μm or more, the effect of forming the first shell section and the second shell section can be basically confirmed. From this viewpoint, the average particle size of the main phase may be 0.2 μm or more, 0.4 μm or more, 0.6 μm or more, 0.8 μm or more, 1.0 μm or more, 2.0 μm or more, 3.0 μm or more, 4.0 μm or more, 5.0 μm or more, 6.0 μm or more, 7.0 μm or more, 8.0 μm or more, or 9.0 μm or more. On the other hand, if the average particle diameter of the main phase is 20 μm or less, the improvement in coercive force due to the formation of the first shell section and the second shell section is greater than the reduction in coercive force due to the increase in size of the main phase. From this viewpoint, the average particle diameter of the main phase may be 18 μm or less, 16 μm or less, 14 μm or less, 12 μm or less, 10 μm or less, 9 μm or less, 8 μm or less, 7 μm or less, 6 μm or less, 5 μm or less, or 4 μm or less.

The "average particle diameter" is measured as follows. A fixed region is defined as viewed from a direction perpendicular to the axis of easy magnetization by using a scanning electron microscopic image or a transmission electron microscopic image, a plurality of lines are drawn in a direction perpendicular to the axis of easy magnetization with respect to a main phase existing in the fixed region, and the diameter (length) of the main phase is calculated from the distance between the point and the point where the main phase intersects within the particles (a cutting method). When the cross section of the main phase is close to a circle, the equivalent diameter of the projected area circle is used for conversion. When the cross section of the main phase is nearly rectangular, the conversion is performed by a rectangular parallelepiped approximation. D of the distribution (particle size distribution) of the diameters (lengths) thus obtained₅₀The value of (b) is an average particle diameter. As shown in fig. 2, the primary phase 10 of the rare earth magnet 500 of the present disclosure has a core portion 20, a first shell portion 30, and a second shell portion 40, and thus the length of the diameter of the primary phase 10 is the diameter (length) encompassing the first shell portion 30 and the second shell portion 40.

Core part

As shown in fig. 2, the core portion 20 exists in the primary phase 10, surrounded by the first and

second shell portions

30 and 40.

The first modification material and the second modification material are not yet diffused and impregnated into the core portion. Therefore, the composition and crystal structure of the core portion are the same as those of the main phase 10 of the second rare earth magnet precursor 100 shown in fig. 1A.

First shell part

As shown in FIG. 2, the first shell portion 30 exists around the core portion 20. In addition, a second shell portion 40 is also present around the first shell portion 30. That is, the first shell portion 30 exists between the core portion 20 and the second shell portion 40. The composition and crystal structure of the first shell portion will be described later.

The first shell portion 30 is formed by diffusion-infiltrating the second modification material 200 into the second rare-earth magnet precursor 100 (refer to fig. 1A and 1B), and further diffusion-infiltrating the first modification material 300 (refer to fig. 1C and 1D).

By diffusion and permeation of the second modification material 200, a part of the light rare earth element existing in the vicinity of the surface layer portion of the main phase 10 is discharged to the grain boundary phase 50. Then, a part of Nd and/or Pr in the melt of the second modifier 200 diffused and infiltrated through the grain boundary phase 50 is taken into the vicinity of the surface layer portion of the main phase 10, thereby forming the first shell portion 30. The second modification material 200 remains as the core portion 20 without diffusion and penetration and without forming the first shell portion 30. Further, a part of the light rare earth element and a part of Nd and/or Pr present in the vicinity of the surface layer of the first shell section 30 are discharged to the grain boundary phase 50 by diffusion permeation of the first modifier 300, and a part of the heavy rare earth element in the melt of the first modifier 300 diffused and permeated through the grain boundary phase 50 is taken in the vicinity of the surface layer portion of the first shell section 30 to form the second shell section 40. The first shell portion 30 is formed by such a displacement, and thus the crystal structure of the first shell portion 30 maintains R₂Fe₁₄And (B) type. Therefore, after diffusion permeation of the second modification material 200 and the first modification material 300, the proportion of Nd and/or Pr present in the first shell portion 30 is higher than that in the core portion 20. I.e., the first shell portion 30The total molar ratio of Nd and Pr in (b) is higher than the total molar ratio of Nd and Pr in the core portion 20.

Basically, the core portion 20 and the first shell portion 30 can be distinguished from each other if the sum of the molar ratios of Nd and Pr in the first shell portion 30 is 1.2 times or more the sum of the molar ratios of Nd and Pr in the core portion. When the heavy rare earth element is diffused and impregnated with the first modified material 300, Nd and/or Pr are substituted with the heavy rare earth element in the vicinity of the surface layer portion of the first shell portion 30, and the second shell portion 40 can be formed. From such a viewpoint, the total of the molar ratios of Nd and Pr in the first shell portion 30 may be 1.4 times or more, 1.6 times or more, or 1.8 times or more the total of the molar ratios of Nd and Pr in the core portion. On the other hand, if the total of the molar ratios of Nd and Pr in the first shell portion 30 is 3.0 times or less the total of the molar ratios of Nd and Pr in the core portion, it is possible to avoid diffusion and penetration of the unnecessary first reforming material 300. From this viewpoint, the total of the molar ratios of Nd and Pr in the first shell portion 30 may be 2.8 times or less, 2.6 times or less, 2.4 times or less, 2.2 times or less, and 2.0 times or less the total of the molar ratios of Nd and Pr in the core portion.

The compositions of the core section 20 and the first shell section 30 were determined based on the results of component analysis using a Transmission Electron Microscope equipped with a Spherical Aberration correction function (Cs-STEM-EDX: Correct-thermal absorption-Scanning Transmission Electron Microscope-Energy Dispersive X-ray Spectrometry). This is because it is difficult to separately observe the core portion 20 and the first shell portion 30 in an Energy Dispersive X-ray spectrometer (SEM-EDX: Scanning Electron Microscope-Energy Dispersive X-ray spectrometer) of a Scanning Electron Microscope.

The thickness of the first shell portion may be appropriately determined according to the relationship with the composition of the first shell portion and the like, and is not particularly limited. The thickness of the first shell portion may be, for example, 30nm or more, 50nm or more, 100nm or more, 150nm or more, 200nm or more, 250nm or more, 300nm or more, 350nm or more, or 400nm or more, or 1000nm or less, 900nm or less, 800nm or less, 700nm or less, 600nm or less, or 500nm or less.

The thickness of the first shell portion is a distance separating an outer circumference of the core portion and an outer circumference of the first shell portion. The method for measuring the thickness of the first shell portion is determined by defining a predetermined region, measuring the separation distances between the main phases existing in the predetermined region using a scanning electron microscope or a transmission electron microscope, and averaging the separation distances.

Second shell part

As shown in FIG. 2, the second shell portion 40 exists around the first shell portion 30.

The second shell portion 40 is formed by diffusion-infiltrating the first modification material 300 into the first rare earth magnet precursor 150 in which the first shell portion 30 is formed (refer to fig. 1C and 1D). When the first modification material 300 is diffusion-infiltrated, a portion of the light rare earth element and a portion of Nd and/or Pr present in the vicinity of the surface layer of the first shell portion 30 are discharged to the grain boundary phase 50. Then, a part of the heavy rare earth element in the melt of the first modifier 300 diffused and infiltrated through the grain boundary phase 50 is taken into the vicinity of the surface portion of the first shell portion 30 to form the second shell portion 40. The second shell portion 40 is formed by such a displacement, and thus the crystal structure of the second shell portion 40 maintains R₂Fe₁₄And (B) type. Thereby, the existing ratio of Nd and/or Pr in the second shell portion 40 is reduced as compared to that in the first shell portion 30. That is, the total of the molar ratios of Nd and Pr in the second shell portion 40 is lower than the total of the molar ratios of Nd and Pr in the first shell portion 30. The second shell portion 40 contains a heavy rare earth element, i.e., one or more elements selected from Gd, Tb, Dy, and Ho. The total content ratio of one or more elements selected from Gd, Tb, Dy, and Ho in the second shell portion 40 as a whole may be 0.15 or more, 0.20 or more, 0.22 or more, or 0.25 or more, and may be 0.45 or less, 0.40 or less, 0.34 or less, 0.32 or less, or 0.30 or less, as represented by a molar ratio.

The core portion 20 and the first shell portion 30 are substantially free of Gd, Tb, Dy, and Ho, excluding the case where mixing from raw materials and the like is unavoidable. Therefore, the total molar ratio of Gd, Tb, Dy, and Ho in the second shell portion 40 is higher than the total molar ratio of Gd, Tb, Dy, and Ho in the core portion 20. The total molar ratio of Gd, Tb, Dy, and Ho in the second shell portion 40 is higher than the total molar ratio of Gd, Tb, Dy, and Ho in the first shell portion 30. Therefore, the total of the molar ratios of Gd, Tb, Dy, and Ho in the second shell portion 40 is 2.0 times or more the total of the molar ratios of Gd, Tb, Dy, and Ho in the core portion 20. The total molar ratio of Gd, Tb, Dy, and Ho in the second shell portion is 2.0 times or more the total molar ratio of Gd, Tb, Dy, and Ho in the first shell portion. The upper limit of the magnification is not specified, and as described above, Gd, Tb, Dy, and Ho can be substantially eliminated from the core section 20 and the first shell section 30, excluding the case where mixing from raw materials and the like is unavoidable. Therefore, the magnification becomes infinite.

If the diffusion permeation amount of the first modified material 300 is large, the total of the molar ratios of Gd, Tb, Dy, and Ho in the grain boundary phase 50 is higher than the total of the molar ratios of Gd, Tb, Dy, and Ho in the second shell portion 40. However, in the grain boundary phase 50, even if Gd, Tb, Dy, and Ho are high, contribution to improvement of the anisotropic magnetic field and residual magnetization is low. In addition, Gd, Tb, Dy, and Ho are heavy rare earth elements and have high rarity, and therefore, it is preferable that the diffusion permeation amount of the first modified material 300 is the minimum necessary amount. Therefore, the total molar ratio of Gd, Tb, Dy, and Ho in the second shell portion 40 is preferably higher than the total molar ratio of Gd, Tb, Dy, and Ho in the grain boundary phase 50. The total molar ratio of Gd, Tb, Dy, and Ho in the second shell portion 40 may be 1.5 times or more, 2.0 times or more, 2.2 times or more, 2.5 times or more, 3.0 times or more, 3.5 times or more, or 4.0 times or more, and may be 8.0 times or less, 6.0 times or less, or 5.0 times or less of the total molar ratio of Gd, Tb, Dy, and Ho in the grain boundary phase 50.

If the sum of the molar ratios of Nd and Pr in the second shell portion 40 is 0.5 times or more the sum of the molar ratios of Nd and Pr in the first shell portion 30, the entire region of the first shell portion 30 is not replaced with the heavy rare earth element upon diffusion penetration of the first modification material 300. If the entire region of the first shell portion 30 is replaced with the heavy rare earth element, only the first shell portion 30 near the surface layer portion (the contact surface with the first modification material 300) of the first rare earth magnet precursor 150 is replaced with the heavy rare earth element. As a result, the heavy rare earth element does not spread inside the rare earth magnet after diffusion and permeation of the first modified material 300, and the improvement of the coercive force of the entire rare earth magnet is prevented. From this viewpoint, the total of the molar ratios of Nd and Pr in the second shell portion 40 may be 0.6 times or more or 0.7 times or more the total of the molar ratios of Nd and Pr in the first shell portion 30.

On the other hand, if the sum of the molar ratios of Nd and Pr in the second shell portion 40 is 0.9 times or less the sum of the molar ratios of Nd and Pr in the first shell portion 30, Nd and/or Pr in the first shell portion 30 can be appropriately substituted with a heavy rare earth element, and the second shell portion 40 can be formed. From this viewpoint, the total of the molar ratios of Nd and Pr in the second shell portion 40 may be 0.8 times or less the total of the molar ratios of Nd and Pr in the first shell portion 30.

The composition of the first shell portion 30 and the second shell portion 40 was determined based on the results of composition analysis using a Transmission Electron Microscope with Spherical Aberration correction function (Cs-STEM-EDX: correct-Spherical Aberration-Scanning Transmission Electron Microscope-Energy Dispersive X-ray Spectrometry). This is because it is difficult to separately observe the first shell portion 30 and the second shell portion 40 in an Energy Dispersive X-ray spectrometer (SEM-EDX: Scanning Electron Microscope-Energy Dispersive X-ray spectrometer) of a Scanning Electron Microscope.

The thickness of the second shell portion may be appropriately determined in accordance with the relationship with the composition of the second shell portion and the like, and is not particularly limited. The thickness of the second shell portion may be, for example, 30nm or more, 50nm or more, 100nm or more, 150nm or more, 200nm or more, 250nm or more, or 300nm or more, or 800nm or less, 700nm or less, 600nm or less, or 500nm or less.

The thickness of the second shell portion is a distance separating an exterior circumference of the first shell portion and an exterior circumference of the second shell portion. The thickness of the second shell portion is measured by defining a predetermined region, measuring the separation distances between the main phases existing in the predetermined region using a scanning electron microscope or a transmission electron microscope, and averaging the separation distances.

Grain boundary phase

As shown in fig. 2, the rare earth magnet 500 of the present disclosure includes a main phase 10 and a grain boundary phase 50 present around the main phase 10. As mentioned above, the main phase 10 comprises a polymer having R₂Fe₁₄Magnetic phase (R) of B-type crystal structure₂Fe₁₄Phase B). On the other hand, the grain boundary phase 50 has R₂Fe₁₄The phase having a crystal structure other than type B includes phases having an undefined crystal structure. By "undefined phase", it is meant, without being bound by theory, a phase (state) in which at least a portion of the phase has an incomplete crystal structure and which exists irregularly. Alternatively, the term "phase (state)" refers to a phase in which at least a part of such a phase (state) hardly has a crystal structure, such as an amorphous phase.

Although the crystal structure of the grain boundary phase 50 is not clear, the composition of the grain boundary phase 50 is such that the proportion of R contained in the entire grain boundary phase 50 is larger than that of the main phase 10 (R)₂Fe₁₄Phase B) is high. Therefore, the grain boundary phase 50 may be referred to as an "R-rich phase", a "rare earth element-rich phase", or a "rare earth element-rich phase".

The grain boundary phase 50 may have R as a triple point (a triple point)_1.1Fe₄B₄And (4) phase(s). The triple point corresponds to a final solidification portion at the time of manufacturing the second rare-earth magnet precursor 100. R_1.1Fe₄B₄There is little contribution to the anisotropic magnetic field (coercive force) and residual magnetization of the rare earth magnet 500 of the present disclosure. Thus, with respect to R_1.1Fe₄B₄In the case of the first modified material 300 and/or the second modified material 200, it is preferable to contain Fe and R_1.1Fe₄B₄Phase transformation to R₂Fe₁₄Phase B is part of the main phase 10.

Manufacturing method

Next, a method for producing the rare earth magnet of the present disclosure will be described.

The disclosed method for producing a rare earth magnet includes a first rare earth magnet precursor preparation step, a first modifying material preparation step, and a first modifying material diffusion infiltration step. As a method for producing the first rare earth magnet precursor, the following two modes are conceivable. The first embodiment is a manufacturing method including a second rare earth magnet precursor preparation step, a second modifier preparation step, and a second modifier diffusion and permeation step. The second embodiment is a manufacturing method including a second rare earth magnet precursor powder preparation step, a second modifier powder preparation step, and a mixed sintering step. The first rare earth magnet precursor preparation step, the first modifier preparation step, and the first modifier diffusion infiltration step are described below, followed by a description of two aspects of the method for producing the first rare earth magnet precursor. As for some matters of the first aspect, international publication No. 2014/196605 can be referred to. In addition, the second embodiment applies a so-called "two-alloy method".

Preparation of first rare earth magnet precursor

As shown in FIG. 1B, the overall composition to be expressed in terms of molar ratio is represented by the formula (R)² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _v·(R³ _(1-p)M² _p)_qA first rare earth magnet precursor 150 is shown. In the formula representing the overall composition of the first rare earth magnet precursor 150, for R¹、R²、R³、Fe、Co、B、M¹And M²And x, y, z, w, v, p and q, as described in "rare earth magnet".

As shown in fig. 1B, the first rare-earth magnet precursor 150 is provided with a main phase 10 and a grain boundary phase 50 present around the main phase 10. The primary phase 10 includes a core 20 and a first shell 30 located around the core 20. As for the compositions and crystal structures of the main phase 10, the core portion 20, and the first shell portion 30, as explained in "rare earth magnet".

In the method for producing a rare earth magnet according to the present disclosure (hereinafter, sometimes referred to as "the production method according to the present disclosure"), the first reforming material 300 is diffused and impregnated into the interior of the first rare earth magnet precursor 150 at a temperature at which the primary phase 10 of the first rare earth magnet precursor 150 is not coarsened, thereby forming the second shell portion 40. Therefore, the average particle diameter of the main phase 10 of the first rare earth magnet precursor 150 is substantially the same size of the range as the average particle diameter of the main phase 10 of the rare earth magnet 500 of the present disclosure. As for the average particle diameter of the main phase 10 of the first rare earth magnet precursor 150 and the composition and crystal structure of the second shell portion 40, as explained in "rare earth magnet".

Preparation of first modified Material

As shown in FIG. 1C, a compound having the formula R in terms of a molar ratio is prepared⁴ _(1-s)M³ _sA first modification material 300 of the composition shown. In the formula representing the composition of the first modified material 300, for R⁴And M³And s as described in "rare earth magnet".

Examples of the method for preparing the first reforming material 300 include a method of obtaining a thin strip from a melt having the composition of the first reforming material 300 by a liquid quenching method, a strip casting method, or the like. In this method, since the melt is rapidly cooled, segregation is small in the first modified material 300. As a method for preparing the first reforming material 300, for example, a melt having a composition of the reforming material is cast in a mold such as a hinge mold (book mold). With this method, a large amount of the first modified material 300 can be obtained relatively easily. In order to reduce the segregation of the first modified material 300, the articulated mold is preferably made of a material having high thermal conductivity. In addition, the cast material is preferably subjected to a homogenization heat treatment to suppress segregation. Further, as a preparation method of the first modified material 300, the following method can be mentioned: a raw material of the first modified material 300 is charged into a vessel, the raw material is arc-melted in the vessel, and the melt is cooled to obtain an ingot. With this method, the first modified material can be obtained relatively easily even when the melting point of the raw material is high. From the viewpoint of reducing the segregation of the first modification material, it is preferable to subject the ingot to a homogenization heat treatment.

Diffusion saturation of first modification material

As shown in fig. 1C, the first modification material 300 is brought into contact with the first rare earth magnet precursor 150, heating both. The diffusion permeation temperature is not particularly limited as long as it is a temperature that enables the first modification material 300 to diffusion permeate into the interior of the first rare-earth magnet precursor 150. The temperature at which the first modification material 300 can be diffusion-impregnated means a temperature at which the second shell portion 40 can be formed without damaging the primary phase 10 (the core portion 20 and the first shell portion 30).

The diffusion permeation temperature of the first modification material may be typically 750 ℃ or more, 775 ℃ or more, or 800 ℃ or more, or 1000 ℃ or less, 950 ℃ or less, 925 ℃ or less, or 900 ℃ or less, in the case where the size of the main phase of the first rare earth magnet precursor is on the micrometer level. The micron level means that the average particle diameter of the main phase is 1 to 20 μm.

The diffusion permeation temperature of the first modification material may be typically 600 ℃ or higher, 650 ℃ or higher, or 675 ℃ or higher, or 750 ℃ or lower, 725 ℃ or lower, or 700 ℃ or lower, in the case where the main phase of the first rare earth magnet precursor has been nano-crystallized. The term "nanocrystalline" means that the average particle size of the main phase is 0.1 to 1.0 μm, particularly 0.1 to 0.9. mu.m.

As shown in fig. 1C, the first shell portion 30 is formed at the primary phase 10 of the first rare earth magnet precursor 150. Also, as shown in fig. 1A and 1B, the second modification material 200 is diffusion-impregnated into the second rare earth magnet precursor 100, forming the first shell portion 30. As shown in fig. 1C and 1D, when the first modification material 300 is diffusion-infiltrated into the interior of the first rare earth magnet precursor 150 to form the second shell portion 40, the first shell portion 30 is further diffusion-infiltrated at a temperature that does not damage the first shell portion 30, within the above-described temperature range for avoiding coarsening of the primary phase 10. For this reason, it is preferable that the diffusion permeation temperature of the first modification material 300 is lower than the diffusion permeation temperature of the second modification material 200. Specifically, the diffusion permeation temperature of the second modification material 200 is set to M_aSetting the diffusion permeation temperature of the first modified material to M DEG C_bAt DEG C, M_a-M_bCan be at least 10 ℃, at least 20 ℃, at least 25℃,40 ℃ or higher, or 50 ℃ or higher, preferably 200 ℃ or lower, 180 ℃ or lower, 160 ℃ or lower, 150 ℃ or lower, 120 ℃ or lower, or 100 ℃ or lower.

At the time of diffusion permeation of the first modification material 300, t molar parts of the first modification material 300 are brought into contact with the first rare-earth magnet precursor 150 with respect to 100 molar parts of the second rare-earth magnet precursor 100. For t, as described in "rare earth magnet".

After the first modification material 300 is diffusion-impregnated into the interior of the first rare earth magnet precursor 150, it is cooled, resulting in the rare earth magnet 500 of the present disclosure. The cooling rate after diffusion permeation of the first modification material 300 is not particularly limited. From the viewpoint of enhancing the coercive force, the cooling rate may be, for example, 10 ℃/min or less, 7 ℃/min or less, 4 ℃/min or less, or 1 ℃/min or less. From the viewpoint of productivity, the cooling rate may be, for example, 0.1 ℃/min or more, 0.2 ℃/min or more, 0.3 ℃/min or more, 0.5 ℃/min or more, or 0.6 ℃/min or more. The cooling rate described here is a cooling rate of up to 500 ℃.

Method for producing first rare earth magnet precursor

Next, a method for producing the first rare earth magnet precursor will be described as a first embodiment and a second embodiment.

First mode

The first mode of the manufacturing method of the first rare earth magnet precursor is to diffusion-impregnate the second modification material into the inside of the second rare earth magnet precursor to obtain the first rare earth magnet precursor. The first mode of the manufacturing method of the first rare-earth magnet precursor includes: a second rare earth magnet precursor preparation step, a second modifier preparation step, and a second modifier diffusion and permeation step. These steps will be described below.

Preparation of second rare-earth magnet precursor

As shown in FIG. 1A, the overall composition to be expressed in terms of molar ratio is prepared by the formula (R)² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _vThe first of the representationTwo rare earth magnet precursors 100. In the formula representing the overall composition of the second rare earth magnet precursor 100, for R¹、R²Fe, Co, B and M¹And x, y, z, w and v, as described in "rare earth magnet".

As shown in fig. 1A, the second rare-earth magnet precursor 100 is provided with a main phase 10 and a grain boundary phase 50 present around the main phase 10. Since the second modification material 200 has not been diffusion-infiltrated into the primary phase 10 of the second rare earth magnet precursor 100, the first shell portion 30 is not formed, and the primary phase 10 of the second rare earth magnet precursor 100 has not been divided into the core portion 20 and the first shell portion 30. The main phase 10 of the second rare earth magnet precursor 100 has R₂Fe₁₄Crystal structure of form B.

The first rare earth magnet precursor 150 is obtained by diffusing and infiltrating the second modification material 200 into the second rare earth magnet precursor 100 at a temperature at which the main phase 10 of the second rare earth magnet precursor 100 is not coarsened, thereby forming the first shell portion 30. Therefore, the average particle diameter of the main phase 10 of the second rare earth magnet precursor 100 is in a substantially same range of size as the average particle diameter of the main phase 10 of the first rare earth magnet precursor 150. As for the average particle diameter and the crystal structure of the main phase 10 of the second rare earth magnet precursor 100, as described in "rare earth magnet".

The second rare earth magnet precursor can be obtained by using a method for producing a rare earth sintered magnet or a nanocrystalline rare earth magnet.

The term "rare earth sintered magnet" generally means a magnet having R as a constituent₂Fe₁₄A rare earth magnet is obtained by cooling a melt having a composition in which the B phase is a main phase at a rate at which the size of the main phase is on the order of micrometers to obtain a magnetic ribbon, and sintering a compact of a magnetic powder obtained by pulverizing the magnetic ribbon at a high temperature without applying pressure. By compacting magnetic powder in a magnetic field (molding in a magnetic field), anisotropy can be imparted to the sintered rare earth magnet (rare earth sintered magnet). In the present specification, unless otherwise specified, R represents₂Fe₁₄Phase B is defined as having R₂Fe₁₄A magnetic phase of crystal structure of type B.

So-called nano-crystallized rare earthMagnet, generally means that will have R taken₂Fe₁₄A rare earth magnet obtained by cooling a melt having a composition in which the B phase is a main phase at a rate at which the main phase is crystallized to form a magnetic sheet and then sintering the magnetic sheet under low pressure (low-temperature hot pressing). The amorphous phase is heat-treated to obtain a main phase of nano-crystallization. Since it is difficult to impart anisotropy to a magnetic sheet having a main phase of nano-crystallization by molding in a magnetic field, anisotropy is imparted to a sintered body obtained by low-temperature pressure sintering by hot plastic working. Such a magnet is called a thermoplastically processed rare earth magnet.

The method for obtaining the second rare earth magnet precursor is described in the case of a manufacturing method using a rare earth sintered magnet and in the case of a manufacturing method using a nanocrystalline rare earth magnet.

Case of manufacturing method using rare earth sintered magnet

When the second rare earth magnet precursor is obtained by the method for producing a rare earth sintered magnet, the following method can be mentioned, for example.

Will be represented by the formula (R) in terms of molar ratio² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _vThe melt is shown as the main phase (R)₂Fe₁₄B phase) is cooled at a speed of 1 to 20 μm to obtain a magnetic ribbon. The cooling rate for obtaining such a magnetic thin strip is, for example, 1 to 1000 ℃/s. Examples of a method for obtaining a magnetic thin strip at such a cooling rate include a strip casting method and a hinge die casting method. The composition of the melt is substantially the same as the entire composition of the second rare earth magnet precursor, and a loss portion of an element which is sometimes lost in the process of producing the second rare earth magnet precursor can be estimated.

The magnetic thin strip obtained as described above is pulverized, and the obtained magnetic powder is pulverized. The pressing can be carried out in a magnetic field. By compacting the powder in a magnetic field, anisotropy can be imparted to the second rare earth magnet precursor, and as a result, anisotropy can be imparted to the rare earth magnet of the present disclosure. The molding pressure in the powder molding may be, for example, 50MPa or more, 100MPa or more, 200MPa or more, or 300MPa or more, or 1000MPa or less, 800MPa or less, or 600MPa or less. The applied magnetic field may be 0.1T or more, 0.5T or more, 1.0T or more, 1.5T or more, or 2.0T or more, and may be 10.0T or less, 8.0T or less, 6.0T or less, or 4.0T or less. Examples of the pulverization method include a method in which a magnetic thin ribbon is coarsely pulverized and then further pulverized by a jet mill or the like. Examples of the method of coarse pulverization include a method using a hammer mill, a method of hydrogen embrittlement of a magnetic thin strip, and a combination thereof.

The green compact obtained as described above is subjected to pressureless sintering to obtain a second rare earth magnet precursor. In order to sinter the green compact without pressurization to increase the density of the sintered body, sintering is carried out at a high temperature for a long time. The sintering temperature may be, for example, 900 ℃ or higher, 950 ℃ or higher, or 1000 ℃ or higher, and may be 1100 ℃ or lower, 1050 ℃ or lower, or 1040 ℃ or lower. The sintering time may be, for example, 1 hour or more, 2 hours or more, 3 hours or more, or 4 hours or more, or 24 hours or less, 18 hours or less, 12 hours or less, or 6 hours or less. The sintering atmosphere is preferably an inert gas atmosphere in order to suppress oxidation of the green compact during sintering. The inert gas atmosphere includes a nitrogen atmosphere.

With respect to the main phase of the second rare earth magnet precursor, by appropriately making R¹And R²The volume ratio of the main phase to the second rare earth magnet precursor can be controlled by changing the total content ratio y and B, the cooling rate during the production of the magnetic thin strip, and the like.

In the second rare earth magnet precursor, the higher the volume fraction of the main phase, the better, as long as the volume fraction of the grain boundary phase is not too small because the volume fraction of the main phase becomes excessive. If the volume ratio of the main phase of the second rare earth magnet precursor is high, the volume ratio of the main phase of the rare earth magnet of the present disclosure also increases, contributing to an increase in remanent magnetization.

On the other hand, if the volume fraction of the main phase of the second rare earth magnet precursor becomes excessive and the volume fraction of the grain boundary phase becomes too small, the second modifier becomes less likely to diffuse and penetrate into the grain boundary phase without being bound by theory, and formation of the first shell portion is inhibited. As a result, in the rare earth magnet of the present disclosure, both the anisotropic magnetic field (coercive force) and the residual magnetization are significantly reduced.

The volume fraction of the main phase of the second rare-earth magnet precursor may be 90.0% or more, 90.5% or more, 91.0% or more, 92.0% or more, 94.0% or more, or 95.0% or more, from the viewpoint of contributing to improvement of residual magnetization. On the other hand, the volume ratio of the main phase of the second rare-earth magnet precursor may be 97.0% or less, 96.5% or less, or 95.9% or less, from the viewpoint of preventing the volume ratio of the main phase of the second rare-earth magnet precursor from becoming excessive.

Case of manufacturing method using nanocrystalline rare earth magnet

When the second rare earth magnet precursor is obtained by the method for producing a nanocrystalline rare earth magnet, the following method can be mentioned, for example.

Will be represented by the formula (R) in terms of molar ratio² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _vThe melt is shown as the main phase (R)₂Fe₁₄Phase B) is cooled at a speed at which the average particle diameter is 0.1 to 1.0 μm, preferably 0.1 to 0.9 μm, to obtain a magnetic ribbon. The cooling rate for obtaining such a magnetic thin strip is, for example, 10⁵～10⁶DEG C/s. As a method for obtaining a magnetic thin strip at such a cooling rate, for example, a liquid quenching method is mentioned. The composition of the melt is substantially the same as the entire composition of the second rare earth magnet precursor, and a loss portion of an element which is sometimes lost in the process of producing the second rare earth magnet precursor can be estimated.

The magnetic thin strip obtained as described above is subjected to low-temperature pressure sintering. The magnetic thin strip may be coarsely pulverized prior to low-temperature pressure sintering. Examples of the method of coarse pulverization include a method using a hammer mill, a method of hydrogen embrittlement of a magnetic thin strip, and a combination thereof. The temperature at the time of low-temperature pressure sintering may be, for example, 550 ℃ or higher, 600 ℃ or higher, or 630 ℃ or higher, or 750 ℃ or lower, 700 ℃ or lower, or 670 ℃ or lower, as long as the main phase is not coarsened. The pressure at the time of low-temperature pressure sintering may be 200MPa or more, 300MPa or more, or 350MPa or more, and may be 600MPa or less, 500MPa or less, or 450MPa or less.

The molded body obtained as described above may be used as it is as a precursor of the second rare earth magnet, or the molded body may be subjected to thermoplastic processing to impart anisotropy to the precursor of the second rare earth magnet. By doing so, anisotropy can be imparted to the rare earth magnet of the present disclosure. The temperature during the thermoplastic processing may be, for example, 650 ℃ or higher, 700 ℃ or higher, or 720 ℃ or higher, or 850 ℃ or lower, 800 ℃ or lower, or 770 ℃ or lower, as long as the main phase is not coarsened. The pressure at the time of thermoplastic processing may be, for example, 200MPa or more, 300MPa or more, 500MPa or more, 700MPa or more, or 900MPa or more, 3000MPa or less, 2500MPa or less, 2000MPa or less, 1500MPa or less, or 1000MPa or less. The reduction ratio may be 10% or more, 30% or more, 50% or more, 60% or more, and may be 75% or less, 70% or less, or 65% or less. The deformation rate at the time of thermoplastic processing may be 0.01/s or more, 0.1/s or more, 1.0/s or more, or 3.0/s or more, and may be 15.0/s or less, 10.0/s or less, or 5.0/s or less.

The control of the volume ratio of the main phase with respect to the second rare earth magnet precursor is the same as in the case of the manufacturing method using the rare earth sintered magnet.

Preparation of the second modified Material

As shown in FIG. 1A, a compound having the formula R in terms of a molar ratio is prepared³ _(1-p)M² _pA second modifying material 200 of the composition shown. In the formula representing the composition of the modifying material, for R³And M²And p, as described in "rare earth magnet".

Examples of the method for preparing the second modifier 200 include a method of obtaining a thin strip from a melt having the composition of the second modifier 200 by a liquid quenching method, a strip casting method, or the like. In these methods, since the melt is quenched, segregation is small in the second modifying material 200. Further, as a method for preparing the second reforming material 200, for example, a molten metal having a composition of the reforming material is cast in a mold such as a hinge mold. With this method, a large amount of the second modified material 200 can be obtained relatively easily. In order to reduce the segregation of the second modification material 200, the articulated mold is preferably made of a material having high thermal conductivity. Further, it is preferable to perform a homogenization heat treatment on the cast material to suppress segregation. Further, as a preparation method of the second modified material 200, the following method can be mentioned: the raw material of the second modifying material 200 is charged into a vessel, the raw material is arc-melted in the vessel, and the melt is cooled to obtain an ingot. With this method, the second modified material can be obtained relatively easily even when the melting point of the raw material is high. From the viewpoint of reducing the segregation of the second reforming material, it is preferable to subject the ingot to a homogenization heat treatment.

Diffusion saturation of the second modification material

The diffusion permeation temperature of the second modifier 200 is not particularly limited as long as the second modifier 200 can diffuse and permeate into the second rare-earth magnet precursor 100. The temperature at which the second reforming material 200 can be diffused and permeated is a temperature at which the primary phase 10 can form the first shell portion 30 without breaking the crystal structure due to coarsening or the like.

The diffusion permeation temperature of the second modifier 200 may be typically 750 ℃ or more, 775 ℃ or more, or 800 ℃ or more, or 1000 ℃ or less, 950 ℃ or less, 925 ℃ or less, or 900 ℃ or less when the size of the main phase 10 of the second rare-earth magnet precursor 100 is on the micrometer level. The micron level means that the average particle diameter of the main phase 10 is 1 to 20 μm.

The diffusion permeation temperature of the second modifier 200 is typically 600 ℃ or higher, 650 ℃ or higher, or 675 ℃ or higher, and may be 750 ℃ or lower, 725 ℃ or lower, or 700 ℃ or lower when the main phase of the second rare-earth magnet precursor 100 is crystallized at 10 nm. The term "nano-crystallization" means that the average particle size of the main phase 10 is 0.1 to 1.0 μm, preferably 0.1 to 0.9. mu.m.

When the second modifier 200 is diffused and impregnated, q parts by mole of the second modifier 200 is brought into contact with 100 parts by mole of the second rare-earth magnet precursor 100 and heated. Q is as described in "rare earth magnet".

After the second modification material 200 is diffusion-impregnated into the second rare earth magnet precursor 100, it is cooled to obtain the first rare earth magnet precursor 150. The cooling rate after diffusion permeation of the second modification material 200 is not particularly limited. From the viewpoint of enhancing the coercive force, the cooling rate may be, for example, 10 ℃/min or less, 7 ℃/min or less, 4 ℃/min or less, or 1 ℃/min or less. From the viewpoint of productivity, the cooling rate may be, for example, 0.1 ℃/min or more, 0.2 ℃/min or more, 0.3 ℃/min or more, 0.5 ℃/min or more, or 0.6 ℃/min or more. The cooling rate described here is a cooling rate of up to 500 ℃.

Second mode

The second mode of the method for producing the first rare earth magnet precursor is to mix the second rare earth magnet precursor powder and the second modifying material powder, and sinter the mixed powder thereof to obtain the first rare earth magnet precursor. A second aspect of the method for producing a first rare earth magnet precursor includes a second rare earth magnet precursor powder preparation step, a second modifier powder preparation step, and a mixed sintering step. These steps will be described below.

Preparation of second rare earth magnet precursor powder

Will have the formula (R) expressed in terms of molar ratio² _(1-x)R¹ _x)_yFe_{(100-y-w-z-v)}Co_wB_zM¹ _vThe melt of the composition shown has a main phase (R)₂Fe₁₄B phase) is cooled at a speed at which the average particle diameter of the B phase) is 0.1 to 20 μm, to obtain a magnetic ribbon. The magnetic thin strip is pulverized to obtain magnetic powder. Examples of the pulverization method include a method in which a magnetic thin ribbon is coarsely pulverized and then further pulverized by a jet mill or the like. Examples of the method of coarse pulverization include a method using a hammer mill, a method of hydrogen embrittlement of a magnetic thin strip, and a combination thereof.

In the representation of meltingIn the formula of the liquid, R¹、R²、Fe、Co、B、M¹And x, y, z, w and v are as described in "rare earth magnet". The composition of the melt is substantially the same as the entire composition of the second rare earth magnet precursor powder, and a loss portion of an element which is sometimes lost in the process of producing the second rare earth magnet precursor powder can be estimated.

The cooling rate of the magnetic ribbon having the main phase with an average particle diameter of 1 to 20 μm is, for example, 1 to 1000 ℃/s. Examples of a method for obtaining a magnetic thin strip at such a cooling rate include a strip casting method and a hinge die casting method. The cooling rate for obtaining a magnetic ribbon having a main phase with an average particle diameter of 0.1 to 1.0 μm, preferably 0.1 to 0.9 μm is, for example, 10⁵～10⁶DEG C/s. As a method for obtaining a magnetic thin strip at such a cooling rate, for example, a liquid quenching method and the like can be cited.

Preparation of the second modified Material powder

Preparing a compound having the formula R expressed by a molar ratio³ _(1-p)M² _pA second modifying material powder of the composition shown. In the formula representing the composition of the modified material powder, for R³And M²And p, as described in "rare earth magnet".

Examples of the method for preparing the second modifier powder include a method of obtaining a thin strip from a melt having a composition of the second modifier powder by a liquid quenching method, a strip casting method, or the like, and crushing the thin strip. In this method, since the melt is rapidly cooled, segregation in the second modifier powder is small. The second modifier powder is prepared by, for example, casting a melt having the composition of the second modifier powder in a mold such as a hinge mold, and pulverizing the cast material. By this method, a large amount of the second modifying material powder can be obtained relatively easily. In order to reduce segregation in the second modifier powder, the articulated mold is preferably made of a material having high thermal conductivity. Further, it is preferable to perform a homogenization heat treatment on the cast material to suppress segregation. Further, as a method for preparing the second modifier powder, the following methods can be mentioned: charging a raw material of the second modifying material powder into a vessel, arc-melting the raw material in the vessel, cooling the melt to obtain an ingot, and pulverizing the ingot. With this method, the second modifier powder can be obtained relatively easily even when the melting point of the raw material is high. From the viewpoint of reducing segregation of the second modifier powder, it is preferable to perform homogenization heat treatment on the ingot in advance.

Mixed sintering

And mixing and sintering the second rare earth magnet precursor powder and the second modifying material powder. After mixing and before sintering, the mixed powder of the second rare earth magnet precursor powder and the second modifying material powder may be pressed.

The compacting may be performed in a magnetic field in the case where the average particle diameter of the main phase in the second rare earth magnet precursor powder is 1 to 20 μm. By compacting in a magnetic field, anisotropy can be imparted to the compact, and as a result, anisotropy can be imparted to the rare earth magnet of the present disclosure. The molding pressure in the powder molding may be, for example, 50MPa or more, 100MPa or more, 200MPa or more, or 300MPa or more, or 1000MPa or less, 800MPa or less, or 600MPa or less. The applied magnetic field may be 0.1T or more, 0.5T or more, 1.0T or more, 1.5T or more, or 2.0T or more, and may be 10.0T or less, 8.0T or less, 6.0T or less, or 4.0T or less.

The green compact obtained as described above is subjected to pressureless sintering to obtain a first rare earth magnet precursor. In order to sinter the green compact without pressurization to increase the density of the sintered body, sintering is carried out at a high temperature for a long time. The sintering temperature may be, for example, 900 ℃ or higher, 950 ℃ or higher, or 1000 ℃ or higher, and may be 1100 ℃ or lower, 1050 ℃ or lower, or 1040 ℃ or lower. The sintering time may be, for example, 1 hour or more, 2 hours or more, 3 hours or more, or 4 hours or more, or 24 hours or less, 18 hours or less, 12 hours or less, or 6 hours or less. The sintering atmosphere is preferably an inert gas atmosphere in order to suppress oxidation of the green compact during sintering. The inert gas atmosphere includes a nitrogen atmosphere.

When the pressureless sintering is performed in this manner, not only the sintered body is simply obtained, but also the second modifier diffuses and penetrates through the grain boundary phase in the second rare-earth magnet precursor powder. The light rare earth element present in the vicinity of the surface layer portion of the main phase is replaced with Nd and/or Pr of the second modifier to form the core portion and the first shell portion, thereby obtaining the first rare earth magnet precursor.

When the average particle diameter of the main phase in the second rare earth magnet precursor powder is 0.1 to 1.0 μm, preferably 0.1 to 0.9 μm, for example, low-temperature pressure sintering is performed without coarsening of the main phase. The temperature at the time of low-temperature pressure sintering may be, for example, 550 ℃ or higher, 600 ℃ or higher, or 630 ℃ or higher, or 750 ℃ or lower, 700 ℃ or lower, or 670 ℃ or lower. The pressure at the time of low-temperature pressure sintering may be 200MPa or more, 300MPa or more, or 350MPa or more, and may be 600MPa or less, 500MPa or less, or 450MPa or less.

The sintered body obtained as described above may be used as it is as a precursor of the second rare earth magnet, or the sintered body may be subjected to thermoplastic processing to impart anisotropy to the precursor of the second rare earth magnet. By doing so, anisotropy can be imparted to the rare earth magnet of the present disclosure. The temperature during the thermoplastic processing may be, for example, 650 ℃ or higher, 700 ℃ or higher, or 720 ℃ or higher, or 850 ℃ or lower, 800 ℃ or lower, or 770 ℃ or lower, as long as the main phase is not coarsened. The pressure at the time of thermoplastic processing may be, for example, 200MPa or more, 300MPa or more, 500MPa or more, 700MPa or more, or 900MPa or more, 3000MPa or less, 2500MPa or less, 2000MPa or less, 1500MPa or less, or 1000MPa or less. The reduction ratio may be 10% or more, 30% or more, 50% or more, 60% or more, and may be 75% or less, 70% or less, or 65% or less. The deformation rate at the time of thermoplastic processing may be 0.01/s or more, 0.1/s or more, 1.0/s or more, or 3.0/s or more, and may be 15.0/s or less, 10.0/s or less, or 5.0/s or less.

The control of the volume ratio of the main phase to the second rare earth magnet precursor is also the same in the case of using the two-alloy method (second embodiment) as in the case of using the manufacturing method of the rare earth sintered magnet (first embodiment).

Deformation of

In addition to the above, the rare earth magnet and the method for manufacturing the same according to the present disclosure can be variously modified within the scope of the contents described in the patent claims. For example, after diffusing the first modification material into the first rare earth magnet precursor, a heat treatment may be further performed to produce the rare earth magnet of the present disclosure. Without being bound by theory, it is considered that, by this heat treatment, part of the grain boundary phase after diffusion and penetration of the first modifying material is melted without changing the structure of the main phase (without melting), and the melt is solidified, and the solidified product is uniformly coated with the main phase, contributing to improvement of the coercive force.

In order to obtain the above-mentioned coercivity improvement effect, the heat treatment temperature is preferably 400 ℃ or higher, more preferably 425 ℃ or higher, and still more preferably 450 ℃ or higher. On the other hand, the heat treatment temperature is preferably 600 ℃ or less, more preferably 575 ℃ or less, and further preferably 550 ℃ or less, in order to avoid the change in the structure of the main phase.

In order to avoid oxidation of the rare earth magnet of the present disclosure, the heat treatment is preferably performed in an inert gas atmosphere, which contains a nitrogen atmosphere.

The rare earth magnet and the method for producing the same according to the present disclosure will be described in more detail with reference to examples and comparative examples. The rare earth magnet and the method for producing the same according to the present disclosure are not limited to the conditions used in the following examples.

Preparation of the samples

The following procedure was used to prepare samples of examples 1 to 5 and comparative examples 1 to 5.

Preparation of the sample of example 1

As the second rare earth magnet precursor, a composition expressed in terms of a molar ratio of Nd as a whole was prepared_6.6Ce_4.9La_1.6Fe_ba _lB_6.0Cu_0.1Ga_0.3The rare earth sintered magnet is shown. For the second rare earth magnet precursor, anisotropy is imparted by shaping in a magnetic field. To contain Nd_0.9Cu_0.1The second modified material of the alloy was diffusion-impregnated into the second rare earth magnet precursor at 950 ℃ to obtain the first rare earth magnet precursor. For 100 molar parts ofAnd a second rare earth magnet precursor, 4.7 molar parts of the second modifying material being diffused and impregnated. So as to contain Tb_0.82Ga_0.15The first modified material of the alloy was diffusion-impregnated into the first rare-earth magnet precursor at 900 c to obtain the sample of example 1. For 100 molar parts of the second rare earth magnet precursor, 1.5 molar parts of the first modification material is diffusion-impregnated.

Preparation of the sample of example 2

As the second rare earth magnet precursor powder, a powder having an overall composition expressed by the molar ratio of Nd was prepared_6.6Ce_4.9La_1.6Fe_balB_6.0Cu_0.1Ga_0.3The magnetic powder shown. In addition, Nd is contained_0.9Cu_0.1Powder of a second modifying material of the alloy. The second rare earth magnet precursor powder and the second modifying material powder are mixed to obtain a mixed powder. For 100 molar parts of the second rare earth magnet precursor powder, 4.7 molar parts of the second modification material powder are mixed. The mixed powder was molded in a magnetic field and sintered at 1050 ℃ to obtain a first rare earth magnet precursor. Then, the mixture is made to contain Tb_0.82Ga_0.15The first modified material of the alloy was diffusion-impregnated into the first rare-earth magnet precursor at 900 c to obtain the sample of example 2. For 100 molar parts of the second rare earth magnet precursor, 1.5 molar parts of the first modification material is diffusion-impregnated.

Preparation of the sample of example 3

As the second rare earth magnet precursor, a composition expressed in terms of a molar ratio of Nd as a whole was prepared_6.6Ce_4.9La_1.6Fe_ba _lB_6.0Cu_0.1Ga_0.3The thermoplastic processed rare earth magnet is shown. To contain Nd_0.7Cu_0.3The second modified material of the alloy is diffusion-impregnated at 700 ℃ to obtain a first rare earth magnet precursor. For 100 molar parts of the second rare-earth magnet precursor, 5.5 molar parts of the second modification material is diffusion-impregnated. Then, the Nd is contained_0.6Tb_0.2Ga_0.2The first modified material of the alloy was diffusion-impregnated into the first rare earth magnet precursor at 675 deg.c to obtain the sample of example 3.For 100 molar parts of the second rare earth magnet precursor, 1.5 molar parts of the first modification material is diffusion-impregnated.

Preparation of sample of comparative example 1

A sample of comparative example 1 was prepared in the same manner as in example 1, except that the second modifying material was not diffused and impregnated into the second rare earth magnet precursor, but the first modifying material was diffused and impregnated into the second rare earth magnet precursor.

Preparation of sample of comparative example 2

A sample of comparative example 2 was prepared in the same manner as in example 3, except that the second modifying material was not diffusion-impregnated into the second rare earth magnet precursor, but the first modifying material was diffusion-impregnated into the second rare earth magnet precursor.

Preparation of sample of comparative example 3

A sample of comparative example 3 was prepared in the same manner as in example 2, except that a rare earth sintered magnet was prepared as the second rare earth magnet precursor, the second modifier was diffused and impregnated into the second rare earth magnet precursor, and thereafter the first modifier was not diffused and impregnated.

Preparation of sample of comparative example 4

A sample of comparative example 4 was prepared in the same manner as in example 3, except that the first modifying material was not diffused and permeated.

Preparation of the sample of example 4

The sample of example 4 was prepared in the same manner as in example 1, except that the diffusion permeation temperature of the first modification material was 850 ℃.

Preparation of the sample of example 5

The sample of example 5 was prepared in the same manner as in example 1, except that the diffusion permeation temperature of the first modification material was 800 ℃.

Preparation of sample of comparative example 5

The sample of comparative example 5 was prepared in the same manner as in example 1, except that the diffusion permeation temperature of the first modification material was 950 ℃.

Evaluation of

The magnetic properties of each Sample were measured at 300K and 453K using a Vibrating Sample Magnetometer (VSM). Further, for each sample, composition analysis of the core portion, the first shell portion and the second shell portion was performed using STEM-EDX (Scanning Transmission Electron Microscope-Energy Dispersive X-ray Spectroscopy). For the sample of example 1, tissue observation and composition analysis were performed using STEM-EDX. For the sample of comparative example 1, component analysis (area analysis) was performed using SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy). The average particle size of the main phase was determined for each sample by the method described in "rare earth magnet".

The results are shown in tables 1-1 and 1-2. FIG. 3A is a graph showing the results of tissue observation using STEM-EDX for the sample of example 1. Fig. 3B is a graph showing the results of surface analysis of Tb using STEM-EDX for the site shown in fig. 3A. FIG. 3C is a graph showing the results of surface analysis of Ce using STEM-EDX for the sites shown in FIG. 3A. FIG. 3D is a graph showing the results of surface analysis of La using STEM-EDX for the region shown in FIG. 3A. Fig. 3E is a view showing the result of surface analysis of Nd using STEM-EDX for the portion shown in fig. 3A. Fig. 4A is a high-resolution STEM image showing the crystal structure of the < 110 > incident direction of the core portion with respect to the sample of example 1. Fig. 4B is a high-resolution STEM image showing the crystal structure in the < 110 > incident direction of the first shell portion for the sample of example 1. Fig. 4C is a high-resolution STEM image showing the crystal structure in the < 110 > incident direction of the second shell portion for the sample of example 1. FIG. 5 is a graph showing the results of line analysis in the direction of the arrow shown in FIG. 3E using STEM-EDX for the sample of example 1. FIG. 6A is a view showing the results of tissue observation using SEM-EDX for the sample of comparative example 1. Fig. 6B is a graph showing the results of surface analysis of Tb using SEM-EDX for the sites shown in fig. 6A. Fig. 6C is a graph showing the results of surface analysis of Ce using SEM-EDX for the sites shown in fig. 6A. Fig. 6D is a view showing the result of surface analysis of Nd using SEM-EDX for the portion shown in fig. 6A. As for the surface analysis result, a portion having a high concentration of the corresponding element is shown as a bright field.

[ TABLE 1-1 ]

[ TABLE 1-2 ]

As can be understood from tables 1-1 and 1-2, the coercivity of the samples of examples 1 to 5 having the first shell portion and the second shell portion was improved. As can be understood from fig. 3A to 3E, with the sample of example 1, the proportion of Nd present in the first shell portion is higher than that in the core portion, the proportion of Nd present in the second shell portion is lower than that in the first shell portion, and Tb is present in the second shell portion. The same can be understood from fig. 5. As can be understood from fig. 4A to 4C, the core portion, the first shell portion, and the second shell portion all exhibit the same lattice pattern as the sample of example 1, and therefore all of the core portion, the first shell portion, and the second shell portion have R₂Fe₁₄Crystal structure of form B. FIGS. 6A to 6D show that Tb is contained from the lower side of the screen without forming the first shell phase_0.82Ga_0.12As a result of surface analysis of the sample (comparative example 1) in which the modifier of the alloy was diffused and penetrated, it can be understood that Tb was present only at a high concentration on the lower side of the screen and did not reach the inside of the rare earth magnet.

From the above results, the effects of the rare earth magnet and the method for producing the same of the present disclosure can be confirmed.

Claims

1. A rare earth magnet, characterized in that it comprises:

main phase and grain boundary phases existing around said main phase, wherein

The overall composition expressed in molar ratio is represented by the formula (R ² _(1-x) R ¹ _x ) _y Fe _(100-ywzv) Co _w B _z M ¹ _v · (R ³ _(1-p) M ² _p ) _q · (R ⁴ _(1-s) M ³ _s ) _t represents, wherein R ¹ is one or more elements selected from Ce, La, Y and Sc, and R ² and R ³ are selected from Nd and Pr One or more elements, R ⁴ is a rare earth element containing at least one or more elements selected from Gd, Tb, Dy and Ho, and M ¹ is selected from Ga, Al, Cu, Au, Ag, Zn, In and One or more elements of Mn and unavoidable impurity elements, M ² is a metal element other than rare earth elements alloyed with R ³ and inevitable impurity elements, M ³ is other than rare earth elements alloyed with R ⁴ . metallic elements and unavoidable impurity elements, and

0.1≦x≦1.0,

12.0≦y≦20.0,

5.0≦z≦20.0,

0≦w≦8.0,

0≦v≦2.0,

0.05≦p≦0.40,

0.1≦q≦15.0,

0.05≦s≦0.40, and

0.1≦t≦5.0,

The main phase has a crystal structure of R ₂ Fe ₁₄ B type, wherein R is a rare earth element,

The average particle size of the main phase is 0.1-20 μm,

The main phase includes a core portion, a first shell portion existing around the core portion, and a second shell portion existing around the first shell portion,

The sum of the molar ratios of Nd and Pr in the first shell is higher than the sum of the molar ratios of Nd and Pr in the core,

The sum of the molar ratios of Nd and Pr in the second shell is lower than the sum of the molar ratios of Nd and Pr in the first shell,

The second shell portion contains one or more elements selected from Gd, Tb, Dy and Ho,

The sum of the respective molar ratios of Gd, Tb, Dy and Ho in the second shell portion is higher than the sum of the respective molar ratios of Gd, Tb, Dy and Ho in the core portion, and

The sum of the molar ratios of Gd, Tb, Dy, and Ho in the second shell portion is higher than the sum of the molar ratios of Gd, Tb, Dy, and Ho in the first shell portion.

2 . The rare earth magnet according to claim 1 , wherein the x is 0.5≦x≦1.0. 3 .

3. The rare earth magnet according to claim 1 or 2, wherein the R ¹ is one or more elements selected from Ce and La, the R ² and the R ³ are Nd, and the The R ⁴ is one or more elements selected from Tb and Nd.

4 . The rare earth magnet according to claim 1 , wherein: 4 .

The sum of the respective molar ratios of Nd and Pr in the first shell portion is 1.2 to 3.0 times the sum of the respective molar ratios of Nd and Pr in the core portion,

The sum of the molar ratios of Nd and Pr in the second shell is 0.5 to 0.9 times the sum of the molar ratios of Nd and Pr in the first shell,

The sum of the respective molar ratios of Gd, Tb, Dy and Ho in the second shell portion is 2.0 times or more the sum of the respective molar ratios of Gd, Tb, Dy and Ho in the core portion, and

The sum of the respective molar ratios of Gd, Tb, Dy and Ho in the second shell portion is 2.0 times or more the sum of the respective molar ratios of Gd, Tb, Dy and Ho in the first shell portion.

5. The manufacturing method of the rare earth magnet according to claim 1, characterized in that, comprising:

A first rare-earth magnet precursor having a main phase and a grain boundary phase existing around the main phase is prepared, and the overall composition represented by the molar ratio is represented by the formula (R ² _(1-x) R ¹ _x ) _y Fe _(100-ywzv) Co _w B _z M ¹ _v ·(R ³ _(1-p) M ² _p ) _q represents, wherein R ¹ is selected from Ce, La, Y and Sc One or more elements, R ² and R ³ are one or more elements selected from Nd and Pr, M ¹ is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In and Mn elements and unavoidable impurity elements, M ² is a metal element other than rare earth elements alloyed with R ³ and unavoidable impurity elements, and

0.1≦x≦1.0,

12.0≦y≦20.0,

5.0≦z≦20.0,

0≦w≦8.0,

0≦v≦2.0,

0.05≦p≦0.40, and

0.1≦q≦15.0,

The main phase has an R ₂ Fe ₁₄ B-type crystal structure, wherein R is a rare earth element, the main phase has an average particle size of 0.1 to 20 μm, and the main phase includes a core portion and a periphery of the core portion a first shell portion is present, and the sum of the respective molar ratios of Nd and Pr in the first shell portion is higher than the sum of the respective molar ratios of Nd and Pr in the core portion;

Prepare a first modified material, the first modified material has a composition represented by the formula R ⁴ _(1-s) M ³ _s expressed in molar ratio, wherein R ⁴ is at least a compound selected from Gd, Tb, Dy and a rare earth element of one or more elements in Ho, M ³ is a metal element other than a rare earth element alloyed with R ⁴ and an unavoidable impurity element, and 0.05≦s≦0.40; and

The first modification material is diffusion impregnated into the first rare earth magnet precursor.

6. The method for manufacturing a rare earth magnet according to claim 5, further comprising:

A second rare-earth magnet precursor having a main phase and a grain boundary phase existing around the main phase is prepared, and the overall composition represented by the molar ratio is represented by the formula (R ² _(1-x) R ¹ _x ) _y Fe _(100-ywzv) Co _w B _z M ¹ _v represents, wherein R ¹ is one or more elements selected from Ce, La, Y and Sc, and R ² is selected from Nd and Pr One or more elements in, M ¹ is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In and Mn and inevitable impurity elements, and

0.1≦x≦1.0,

12.0≦y≦20.0,

5.0≦z≦20.0,

0≦w≦8.0, and

0≦v≦2.0,

The main phase has an R ₂ Fe ₁₄ B-type crystal structure, wherein R is a rare earth element, and the average particle size of the main phase is 0.1-20 μm;

Prepare a second modified material having a composition represented by the formula R ³ _(1-p) M ² _p expressed in molar ratio, wherein R ³ is one selected from Nd and Pr For the above elements, M ² is a metal element other than a rare earth element alloyed with R ³ and an unavoidable impurity element, and 0.05≦p≦0.40;

The second modified material is diffused and impregnated into the second rare earth magnet precursor to obtain the first rare earth magnet precursor.

7. The method for manufacturing a rare earth magnet according to claim 5, further comprising:

A second rare earth magnet precursor powder having a main phase and a grain boundary phase existing around the main phase is prepared, and the overall composition represented by the molar ratio is represented by the formula (R ² _{(1- x)} R ¹ _x ) _y Fe _(100-ywzv) Co _w B _z M ¹ _v represents, wherein R ¹ is one or more elements selected from Ce, La, Y and Sc, and R ² is selected from Nd and one or more elements of Pr, M ¹ is one or more elements selected from Ga, Al, Cu, Au, Ag, Zn, In and Mn and inevitable impurity elements, and

0.1≦x≦1.0,

12.0≦y≦20.0,

5.0≦z≦20.0,

0≦w≦8.0, and

0≦v≦2.0,

Preparation of a second modifier powder having a composition represented by the formula R ³ _(1-p) M ² _p in molar ratio, wherein R ³ is selected from Nd and Pr One or more elements, M ² is a metal element other than rare earth elements alloyed with R ³ and an unavoidable impurity element, and 0.05≦p≦0.40; and

The second rare earth magnet precursor powder and the second modifying material powder are mixed and sintered to obtain the first rare earth magnet precursor.

8 . The method for manufacturing a rare earth magnet according to claim 6 , wherein the diffusion penetration temperature of the first modification material is higher than that of the second modification material or the second modification material powder. 9 . Diffusion penetration temperature is low.

9 . The method for producing a rare earth magnet according to claim 5 , wherein the x is 0.5≦x≦1.0. 10 .

10 . The method for producing a rare earth magnet according to claim 5 , wherein the R ¹ is one or more elements selected from Ce and La, and the R ² and the R ³ is Nd, and the R ⁴ is one or more elements selected from Tb and Nd.